Microwave dielectric and magnetic properties of superparamagnetic 8-nm Fe3O4 nanoparticles

The superparamagnetic 8-nm Fe₃O₄ nanoparticles were successfully prepared by chemical oxidation process. For the complex permittivity, the dual dielectric relaxation processes have been proved by two overlapped Cole–Cole semicircles, and the natural resonance frequency is 3.03 GHz for the complex permeability. The maximum reflection loss value reaches −55.5 dB at 6.11 GHz with 3.85 mm in the thickness of the absorbers for the superparamagnetic 8-nm Fe₃O₄ nanoparticles which is better than that of 150 nm and 30 nm Fe₃O₄ nanoparticles. It is believed that the superparamagnetic 8-nm Fe₃O₄ nanoparticles can be used as a kind of candidate for microwave absorber.     

Ligation of the quinolone antibacterial agent pipemidic acid to Keggin polyoxotungstates

Three new drug molecules modifying Keggin polyoxometallate compounds have been synthesized under hydrothermal conditions and structurally characterized by routine techniques. Single-crystal X-ray diffraction analysis shows that compound 1 is constructed by a Keggin cluster and two [Cu(PPA)₂] drug complexes, formulated as [Cu(PPA)₂]₂·[PW₁₂O₄₀]·6H₂O. Compound 2 consists of a Cd substituted Keggin cluster [PW₁₁CdO₃₉] and five isolated HPPA drug molecules, formulated as [HPPA]₅·[PW₁₁CdO₃₉]·2H₂O. Compound 3 consists of a full oxidised Keggin [PW₁₂O₄₀] cluster and three isolated HPPA drug molecules, formulated as [HPPA]₃·[PW₁₂O₄₀]·2H₂O. Additionally, the antitumor activity of the three new compounds and their parent components in vitro were studied by a MTT experiment. The results show that introduction of TM-PPA/PPA into the polyoxoanion surface could increase their antitumor activity and make the compounds penetrate into the cells easily. Furthermore, the antitumor activity of the compounds can be modulated by their different structures.     

Synthesis and photochromism of novel unsymmetrical diarylethenes with an azaindole unit

A new class of unsymmetrical photochromic diarylethenes with an azaindole moiety has been firstly synthesized. Their properties, including photochromism, crystal structure, as well as fluorescence, were investigated systematically. The azaindole was connected directly to the central cyclopentene ring as a heteroaryl moiety and available to participate in the photoisomerization reaction. Each of the diarylethenes exhibited favorable photochromism, good thermal stability, remarkable fatigue resistance, and notable fluorescence switches in both solution and solid media. The substituents at the para-position of the terminal benzene ring affected evidently their properties: the electron-donating methoxy could be effective to enhance the cyclization quantum yield, while the electron-withdrawing cyano could shift the absorption maximum to a longer wavelength in both hexane and solid film. The results revealed that the introduction of azaindole moieties and different substituents played an important role in the photoisomerization process of these diarylethenes.     

Spectroscopic investigations on NO＋（X1∑＋, a3∑＋, A1II） ion using multi-reference configuration interaction method and correlation-consistent sextuple basis set augmented with diffuse functions

Three low-lying electronic states （X1∑, a3∑＋, and A1II） of NO＋ ion are studied using the complete active space self-consistent-field （CASSCF） method followed by highly accurate valence internally contracted multi-reference configuration interaction （MRCI） approach in combination of the correlation-consistent sextuple basis set augmented with diffuse functions, aug-cc-pV6Z. The potential energy curves （PECs） of the NO＋（X1∑＋, a3∑＋, A1II） are calculated. Based on the PECs, the spectroscopic parameters Re, De, We, WeXe, ae, Be, and D0 are reproduced, which are in excellent agreement with the available measurements. By numerically solving the radial SchrSdinger equation of nuclear motion using the Numerov method, the first 20 vibrational levels, inertial rotation and centrifugal distortion constants of NO＋（X1∑＋, a3∑＋, A1II） ion are derived when the rotational quantum number J is equal to zero （J = 0） for the first time, which accord well with the available measurements. Finally, the analytical potential energy functions of these states are fitted, which are used to accurately derive the first 20 classical turning points when J = 0. These results are compared in detail with those of previous investigations reported in the literature.     

Ba1－xSrxTiO3的Sol-gel法制备与结构相变研究

采用sol-gel法制备了钛酸锶钡(Ba1－xSrxTiO3)．用XRD、DSC、Raman等表征技术研究了Ba1－xSrxTiO3的晶体结构和相变行为.结果表明,随着锶含量的增加,晶胞体积逐渐减小,c/a趋近于1,相变温度降低,相变热减少,相变弥散性增强,且存在热滞现象.Raman光谱发生有趣变化,当x=0.30时,室温下发生结构相变, Ba1－xSrxTiO3以立方相为主要存在相,相变具有有序-无序特征.     

Adsorption of CO2 on PbO at ambient temperature

The adsorption of CO₂ on metal oxides at ambient temperature received less study largely due to the small adsorption amount. However, the adsorption is of interest in refreshing the atmosphere of isolated spaces. It was shown in the present work that P_bO was sensitive to low concentration CO₂ in the presence of water. An XPS examination indicated that P_bO changed to P_bCO₃ after the adsorption of CO₂; therefore, the adsorption is chemical in nature. In order to enlarge the CO₂ capacity, P_bO was dispersed on the surface of a silica gel with large surface area (710 m²/g). Both CO₂ capacity and adsorption rate indicated that the optimal dispersion manner of P_bO is the mono-molecular layer surface coverage. Breakthrough experiments showed that the prepared adsorbent could effectively capture low-concentration CO₂ at ambient temperature and pressure yielding a CO₂ capacity of 59.1 mg g⁻¹. The saturated adsorbent was regenerated on heating at 380 °C and the CO₂ capability was recovered.