Time-resolved photoluminescence of anatase/rutile TiO_2 phase junction revealing charge separation dynamics

Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO2 phase junction using time-resolved photoluminescence spectroscopy. Visible （-S00 nm） and near-infrared （NIR, -830 nm） emissions were monitored to give insight into the photoinduced charges of anatase and rutile in the junction, respectively, New fast photoluminescence decay components appeared in the visible emission of futile-phase dominated TiO2 and in the NIR emission of many mixed phase TiO2samples. The fast decays confirmed that the charge separation occurred at the phase junction. The visible emission intensity from the mixed phase TiO2 increased, revealing that charge transfer from rutile to anatase was the main pathway. The charge separation slowed the microsecond time scale photolumines- cence decay rate for charge carriers in both anatase and rutile. However, the millisecond decay of the charge carriers in anatase TiO2 was accelerated, while there was almost no change in the charge carrier dynamics of rutile TiO2. Thus, charge separation at the anatase/rutile phase junction caused an increase in the charge carrier concentration on a microsecond time scale, because of slower electron-hole recombination. The enhanced photocatalytic activity previously observed at ana- tase/rutile phase junctions is likely caused by the improved charge carrier dynamics we report here. These findings may contribute to the development of improved photocatalytic materials.

Effect of Lattice Distortion on Charge Order in Manganites at Doping x=0.5

In the present paper, we continue our investigation on the antiferromagneticorigin of the charge order observed in the halt-doped manganese. By introducing aSu-Schrieffer-Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, wecalculate again its ground-state phase diagram at Glling x = 0.5 by the unrestricted real-spaceHartree-Fock approximation method. We find that, as the SSH electron-phonon interaction increases,the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomesmore stable. In other words, the charge order is much more fragile than the CE-type or theNeel-type antiferromagnetic orders under the electron-phonon perturbation. These results support theproposed theory in the recent publications that the charge order in these systems is induced by theantiferromagnetic correlations.

Experimental realization to efficiently sort vector beams by polarization topological charge via Pancharatnam–Berry phase modulation

This paper reports the experimental realization of efficiently sorting vector beams by polarization topological charge （PTC）. The PTC of a vector beam can be defined as the repetition number of polarization state change along the azimuthal axis, while its sign stands for the rotating direction of the polarization. Here, a couple of liquid crystal Pancharatnam-Berry optical dements （PBOEs） have been used to introduce conjugated spatial phase modulations for two orthogonal circular polarization states. Applying these PBOEs in a 4-foptical system, our experiments show the setup can work for PTC sorting with a separation efficiency of more than 58%. This work provides an effective way to decode information from different PTCs, which may be interesting in many fields, especially in optical communication.

Quantum phase transition in quarter-filled nanoclusters of manganite induced by element substitution at B site

In the present paper,we study the effect of element substitution for quarter-filled nanoclusters of perovskite manganite by introducing Jahn-Teller type of perturbation interaction to the double-exchange Hamiltonian.Using the unrestricted real-space Hartree-Fock approximation method we find that,the Jahn-Teller electron-phonon interaction plays the central role in producing the phase transition from ferromagnetic phase to CE type antiferromagnetic phase.Not only the Jahn-Teller interaction benefits antiferromagnetic correlation,it also increases the charge density order parameter.These theoretical results provide a guidance to predict the properties and modify the composition of particles of perovskite manganite under nano-scale.

Determination of total ginsenosides in ginseng extracts using charged aerosol detection with post-column compensation of the gradient

AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.