Two comparable models of BiOI/BiOCl heterojuctions with different interface structures (crystal surface orientation and crystal surface combination), denoted as BiOI(001)/BiOCl(001) and BiOI(001)/BiOCl(010), have been prepared via integrating heterojuncton nanostructure construction with crystal facet engineering. BiOI(001)/BiOCl(010) had a greater degree of lattice mismatch and displayed higher visible-light photocatalytic activity than BiOI(001)/BiOCl(001). In general, the activity of a photocatalyst (ηPC) has a positive correlation with light harvesting (ηLH), charge separation (ηCS), and charge injection (ηCI). On the basis of the experimental results, we considered that the higher ηCI value of BiOI(001)/BiOCl(010) was the main reason for its better visible-light photocatalytic performance. In combination with theoretical calculations, we found that the higher ηCI value of BiOI(001)/BiOCl(010) was the result of a shorter photogenerated electron diffusion distance, assisted by the self-induced internal electric fields of the BiOCl slabs. This indicated that the crystal facet combination is the key to enhancing the photocatalytic activity of BiOI/BiOCl. Our work offers an archetype for the further design of heterojunction photocatalysts with a fine tuning of the interface structures in order to reach optimized charge injection and enhanced photocatalytic activity.

The vibrationally resolved electronic circular dichroism (ECD) spectra of the two dominant conformers of (R)-(+)-3-methylcyclopentanone in gas phase are computed by density functional response theory, with a full account of Franck-Condon and Herzberg-Teller vibrational contributions at the harmonic level. Proper inclusion of the latter contributions was made possible by the recent implementation of effective-scaling computations of vibrational overlaps and of analytical gradients of time dependent DFT. The Coulomb-attenuated Becke three parameters Lee-Yang-Parr (CAM-B3LYP) functional reproduces both the position and the intensity of the experimental peaks, providing a remarkable improvement over the spectra obtained with the popular hybrid B3LYP functional, and allowing a confident assignment of the CD fine vibrational structure. Franck-Condon and Herzberg-Teller contributions are discussed in detail. The computed decrease of the CD intensity in the gas phase upon increase of the temperature of the sample follows the trend observed experimentally in different solvents.

We present a systematic investigation of the microscopic mechanism of interface interaction, charge transfer and separation, as well as their influence on the photocatalytic activity of heterojunctions by a combination of theoretical calculations and experimental techniques for the g-C 3 N 4 -ZnWO 4 composite. HRTEM results and DFT calculations mutually validate each other to indicate the reasonable existence of g-C 3 N 4 (001)-ZnWO 4 (010) and g-C 3 N 4 (001)-ZnWO 4 (011) interfaces. The g-C 3 N 4 -ZnWO 4 heterojunctions show higher photocatalytic activity for degradation of MB than pure g-C 3 N 4 and ZnWO 4 under visible-light irradiation. Moreover, the heterojunctions significantly enhance the oxidation of phenol in contrast to pure g-C 3 N 4 , the phenol oxidation capacity of which is weak, clearly demonstrating a synergistic effect between g-C 3 N 4 and ZnWO 4 . Interestingly, based on the theoretical calculations, we find that electrons in the upper valence band can be directly excited from g-C 3 N 4 to the conduction band, that is, the W 5d orbital of ZnWO 4 , under visible-light irradiation, which should yield well-separated electron-hole pairs, with high photocatalytic performance in g-C 3 N 4 -ZnWO 4 heterojunctions as shown by our experiment. The microcosmic mechanisms of interface interaction and charge transfer in this system can be helpful for fabricating other effective heterostructured photocatalysts.

Titanium dioxide (TiO 2 ) codoped with bismuth (Bi) and sulfur (S) elements was prepared by a simple solgel method using tetrabutyl titanate, bismuth nitrate pentahydrate, and thiourea as precursors. The codoped TiO 2 calcined at 400 °C exhibits an intense absorption in the range of 500-800 nm. The absorption edge corresponds to a band gap of 2.0 eV. An indigo carmine solution of 20 mg/L was completely photodegraded in 40 min in the presence of such photocatalyst under visible light (λ > 410 nm). This highly active photocatalytic performance is associated with the existence of numerous oxygen vacancies, the acidic sites on the surface of TiO 2 , and the high specific surface area.

Heck coupling reactions are introduced as an efficient method to prepare porous polymers. Novel inorganic-organic hybrid porous polymers (HPPs) were constructed via Heck coupling reactions from cubic functional polyhedral oligomeric silsesquioxanes (POSS), iodinated octaphenylsilsesquioxanes (OPS) and octavinylsilsesquioxanes (OVS) using Pd(OAc)2 /PPh3 as the catalyst. Here, two iodinated OPS were used, IOPS and p-I8 OPS. IOPS was a mixture with 90% octasubstituted OPS (I8 ) and some nonasubstituted OPS (I9 ), while p-I8 OPS was a nearly pure compound with ≥99% I8 and ≥93% para-substitution. IOPS and p-I8 OPS reacted with OVS to produce the porous materials HPP-1 and HPP-2, which exhibited comparable specific surface areas with SBET of 418 ± 20 m(2) g(-1) and 382 ± 20 m(2) g(-1) , respectively, with total pore volumes of 0.28 ± 0.01 cm(3) g(-1) and 0.23 ± 0.01 cm(3) g(-1) , respectively. HPP-1 showed a broader pore size distribution and possessed a more significant contribution from the mesopores, when compared with HPP-2, thereby indicating that IOPS may induce more disorder because of the geometrical asymmetry. HPP-1 and HPP-2 possessed moderate carbon dioxide uptakes of 134 and 124 cm(3) g(-1) at 1 bar at 195 K, making them promising candidates for CO2 capture and storage. The synthesized porous polymers may be easily post-functionalized using the retained ethenylene groups.

The mechanism of oil detachment from solid surfaces in aqueous surfactant solutions is studied by molecular dynamics simulations. At the initial simulation, the hydrophilic silica surface changes into a hydrophobic one due to the adsorption of the alkane molecules. Two-dimensional ordered arrangement of alkane molecules on the first layer is the key to the oil detachment from the silica surface. Upon addition of cetyltrimethylammonium bromide (CTAB) solution, the alkane molecules on the solid surface can be detached from a hydrophilic silica surface. Ultimately, the silica surface becomes hydrophilic, and the oil molecules are solubilized in the surfactant micelles. During the process of oil detachment, it is demonstrated that the formation of a water channel in the oil phase between the surfactant solution and the silica surface is vital for the oil detachment. Meanwhile, water molecules can penetrate the oil-water interface by diffusion and form the gel layer at the water-silica interface under the hydrogen-bonding and electrostatic interaction, in the close vicinity of the contact line. Both of these will accelerate the removal of the oil molecules from the silica surface under the surfactant solution. According to the energy and configurations with time evolution, one three-stage model of oil detachment from the silica surface is developed at the molecular level. The simulation results agree with the experimental phenomenon.

A harmonic adiabatic approach in combination with density functional response theory for computing two-photon vibronically resolved circular dichroism spectra of chiral molecules is presented. It includes both Franck-Condon and Herzberg-Teller contributions and it takes fully into account frequency changes and Duschinsky effects. Model calculations have been performed for two dominant conformers of (R)-(+)-3-methylcyclopentanone in the gas phase. It is found that the Herzberg-Teller contribution can introduce a sign change in two-photon circular dichroism of a single excited electronic state of a conformer. The change survives after Boltzmann averaging, and it might be amenable to experimental verification. Interesting interference effects between Franck-Condon and Herzberg-Teller contributions are revealed and analyzed in detail. Results obtained within the more approximate and less computationally intensive linear coupling vibronic model are also given for comparison.

First-principles calculations have been performed to determine the effects of Ag doping to the structural, electronic, and optical properties of ZnO NWs. The calculated formation energies are very low for Ag dopants at substitutional-Zn sites (both under low and high Ag concentration), but rather high at substitutional-O and interstitial sites under O-rich conditions. The Ag Zn and 2Ag Zn defects all prefer the edge of the NW and the formation energy of 2Ag Zn in the favorable O-rich conditions is only 0.40 eV. The calculated acceptor levels of Ag Zn and 2Ag Zn ones are 0.60 and 0.44 eV respectively, indicating Ag may be a good candidate for producing p-type ZnO NW. From the optical properties calculations, strong absorptions have been found in the visible-light region for both the 2Ag Zn and Ag O -doped ZnO NWs. It provides evidence that, except for the usage as short-wavelength optoelectronic devices, Ag-doped ZnO NWs could also display potential application for photocatalysis due to the increase of the visible-photocatalytic activity.