We measured the water content （0.01% 0.25% w/w） in crude oil emulsions using terahertz time-domain spectroscopy （THz-TDS）. To improve the precision and range of the measurements, we used 1 and 10 mm thick quartz cells. The experiments were performed at 20 ℃ and the THz wave was transmitted vertically to the samples and detected on the other side. The experimental results suggest linear relation for the THz absorption coefficient and the water content of the crude oil emulsions in the observed range. The linear dependence facilitates high-precision measurements of the water content of crude oil. This suggests the potential of THz-TDS in determining the water concentration in crude oil and borehole fluid identification.
Terahertz time-domain spectroscopy （THz-TDS） is used to study the interaction between AlCl3 and o-xylene in a temperature range from 300 K to 368 K. For comparison, the three isomers of o-, m-, and p-xylene are measured by using THz-TDS. The o-xylene carries out isomerization reaction in the presence of catalyst AlCl3. The absorption coefficient of the mixed reaction solution is extracted and analyzed in the frequency range from 0.2 THz to 1.4 THz. The temperature dependence of the absorption coefficient, which is influenced by both the dissolution of AlCl3 and the production of the two other isomer resultants, is obtained, and it can indicate the process of the isomerization reaction. The results suggest that THz spectroscopy can be used to monitor the isomerization reaction and other reactions in chemical synthesis, petrochemical and biomedical fields.
Iridium complexes with dicyanovinyl-grafted phenylpyridine/l-phenylisoquinoline as ligands are synthesized and their photo- physical, electrochemical, and sensitization properties in DSSCs are investigated. The iridium complexes present significantly enhanced absorption from 400 to 525 nm. The 1-phenylisoquinoline-based iridium complex show bathochromic-shift emission in DMSO solution compared with their phenylpyridine-based counterpart, while their absorption response and photoluminescence peak in solid show little difference despite extension of the conjugated system. Using DSSCs, the conversion efficiency of 0.62% and open-circuit current of 1.4 mA/cm2 is achieved. The poor performance is attributed to the excited-state properties of iridium complexes according to the TD-DFT calculation.
Dongdong WangHua DongXiaoyu ZhangYong WuShaohua ShenBo JiaoZhaoxin WuMin GaoGeng Wang
The ultrafast laser-excited magnetization dynamics of ferromagnetic （FM） La0.67Sr0.33MnO3 （LSMO） thin films with BiFeO3 （BFO） coating layers grown by laser molecular beam epitaxy are investigated using the optical pump-probe technique. Uniform magnetization precessions are observed in the films under an applied external magnetic field by measuring the time-resolved magneto-optical Kerr effect. The magnetization precession frequencies of the LSMO thin films with the BFO coating layers are lower than those of uncoated LSMO films, which is attributed to the suppression of the anisotropy field induced by the exchange interaction at the interface between the antiferromagnetic order of BFO and the FM order of LSMO.
Qian WanKuiJuan JinJieSu WangHongBao YaoJunXing GuHaiZhong GuoXiuLai XuGuoZhen Yang
Terahertz time-domain spectroscopy (THz-TDS) has been used to probe the evolutionary paths of kerogen in selected black mudstone. The evolutionary regime of kerogens (for instance, the immaturity, early maturity, middle maturity, late maturity, and catagenesis stages) can be indicated by the absorption coefficient in the THz region. The present study of identification based on THz-TDS was in good agreement with programmed pyrolysis experiments and suggests that THz technology can act as a nondestructive, contact-free tool for probing the ability to generate hydrocarbons from kerogens.
BAO RiMaWU ShiXiangZHAO KunZHENG LunJuXU ChangHong
The symmetry of the surfaces of SrTiO3 and slightly Nb-doped SrTiO3 crystals was investigated by the optical reflected second harmonic generation technique. The good agreement between experimental and theoretical results of the second harmonic in- tensity dependence on the azimuth angle indicates that the SrTiO3 （001） surface is with 4ram symmetry and the Nb-doped SrTiO3 （111） surface with 3m symmetry. The measurements of the polarization dependent second harmonic intensity confirm that conclusion. The enhancement of the surface polarization in the structure of SrTiO3 capped La0.9Sr0.1MnO3 films compared with that in the La0.9Sr0.1MnO3 films has been obtained.
Varying the film thickness is a precise route to tune the interfacial strain to manipulate the properties of the multiferroic materials.Here,to explore the effects of the interfacial strain on the properties of the multiferroic BiFeO_3films,we investigated thickness-dependent structural and polarization evolutions of the BiFeO_3 films.The epitaxial growth with an atomic stacking sequence of BiO/TiO_2 at the interface was confirmed by scanning transmission electron microscopy.Combining X-ray diffraction experiments and first-principles calculations,a thickness-dependent structural evolution was observed from a fully strained tetragonality to a partially relaxed one without any structural phase transition or rotated twins.The tetragonality(c/a) of the BiFeO_3 films increases as the film thickness decreases,while the polarization is in contrast with this trend,and the size effect including the depolarization field plays a crucial role in this contradiction in thinner films.These findings offer an alternative strategy to manipulate structural and polarization properties by tuning the interfacial strain in epitaxial multiferroic thin films.
郭海中Ruiqiang ZhaoKui-juan JinLin GuDongdong XiaoZhenzhong YangXiaolong LiLe WangXu HeJunxing GuQian WanCan WangHuibin LuChen GeMeng HeGuozhen Yang
Switchable diode effect in ferroelectric diodes has attracted much attention for its potential applications in novel nonvolatile memories. We briefly review recent investigations on the switchable diode effect in ferroelectric diodes both experimentally and theoretically. Many recent studies demonstrate that the interfacial barrier between the metal-ferroelectrics could be modulated by the polarization charges, and the ferroelectric polarization that can be reversed by an external electric field plays a dominant role in the switchable diode effect. Moreover, we review a self-consistent numerical model, which can well describe the switchable diode effect in ferroelectric diodes. Based on this model, it can be predicted that it is a better choice to select metals with a smaller permittivity, such as noble metals, to obtain a more pronounced switchable diode effect in ferroelectric diodes.
Chen GeCan WangKui-juan JinHui-bin LuGuo-zhen Yang
