RESUMO
An outstanding advantage of inorganic ceramic ferroelectrics is their usability in the polycrystalline ceramic or thin film forms, which has dominated applications in the ferroelectric, dielectric, and piezoelectric fields. Although the history of ferroelectrics began with the molecular ferroelectric Rochelle salt in 1921, so far there have been very few molecular ferroelectrics, with lightweight, flexible, low-cost, and biocompatible superior properties compared to inorganic ceramic ferroelectrics, that can be applied in the polycrystalline form. Here, a multiaxial molecular ferroelectric, guanidinium perchlorate ([C(NH2 )3 ]ClO4 ), with a record-high phase transition temperature of 454 K is presented. It is the rectangular polarization-electric field (P-E) hysteresis loops recorded on the powder and thin film samples (with respective large Pr of 5.1 and 8.1 µC cm-2 ) that confirm the ferroelectricity of [C(NH2 )3 ]ClO4 in the polycrystalline states. Intriguingly, after poling, the piezoelectric coefficient (d33 ) of the powder sample shows a significant increase from 0 to 10 pC N-1 , comparable to that of LiNbO3 single crystal (8 pC N-1 ). This is the first time that such a phenomenon has been observed in molecular ferroelectrics, indicating the great potential of molecular ferroelectrics being used in the polycrystalline form like inorganic ferroelectrics, as well as being viable alternatives or supplements to conventional ceramic ferroelectrics.
RESUMO
It is known that CH3NH3PbI3 is particularly promising for next-generation solar devices; therefore, molecular perovskite structures have recently received extraordinary attention from the academic community because of their potential in producing unique physical properties. However, although great efforts have been made, molecular ferroelectrics with three-dimensional (3D) perovskite structures are still rare. So far, reported perovskite-like molecular ferroelectrics are basically one- or two-dimensional, significantly deviating from the inorganic perovskite ferroelectrics. Thus, their ferroelectric properties have to be greatly improved to meet the requirements of practical applications. Here, we report a 3D molecular perovskite ferroelectric: (3-ammoniopyrrolidinium)RbBr3 [(AP)RbBr3], with a high Curie temperature (Tc = 440 K) beyond that of BaTiO3. To the best of our knowledge, such above-room-temperature ferroelectricity in the 3D molecular perovskite compound is unprecedented. Furthermore, (AP)RbBr3 has great potential for applications due to its high thermal stability, ultrafast polarization reversal (greater than 20 kHz), and fascinating multiaxial characteristic. This finding opens a new avenue to the design and controllable synthesis of molecular ferroelectric perovskites, where the metal ion, halogen ion, and organic cation can be easily tuned.
RESUMO
OBJECTIVE: To investigate the effect of compound Danshen Dripping Pill (DSP) on carotid arterial intima-media thickness (IMT) in patients with type 2 diabetes mellitus (T2DM). METHODS: One hundred and thirty T2DM patients were assigned to four groups, 32 in the Group A, the control group treated with blood glucose (BG) and blood pressure (BP) controlling; 32 in the Group B, with BG, BP and blood lipid (BL) controlling, 32 in Group C with BG, BP, BL controlling and vitamin E administration, and 34 in Group D with BG, BP, BL controlling and DSP administration. Patients in Group D were subdivided by Chinese medicine syndrome differentiation into four types, 8 of Yin-deficiency with flourishing heat type (YDFH), 5 of both qi-yin deficient type (BQYD), 8 of both yin-yang deficient type (BYYD) and 13 of blood-stasis and qi-stagnant type (BSQS). Fasting blood glucose (FBG), BP and BL in patients were observed periodically, and IMT in them were measured by ultrasonography before treatment, as well as at the end of the 1st, 3rd, and 5th year of treatment to dynamically observe the changes of IMT and condition of plaque formation, and analyze the relation between them with FBG, BP and BL. RESULTS: The 5-year follow-up was performed in 105 patients. In the observation period, level of total cholesterol (TC) showed a decreasing trend and level of high density cholesterol (HDL-C) showed an increasing trend in all the 4 groups, the improvements in Group C and D were slightly better than those in Group B, while significantly superior to those in Group A; the changes of FBG and glycosylated hemoglobin (HbAlc) were insignificant in the 4 groups. IMT and numbers of atheroma plaque increased gradually in all groups in the observation period, however, the changes in Group D were lesser than those in other groups, showing significant difference (P < 0.01). It was showed that the increasing of cervical carotid IMT in T2DM patients was correlated with levels of HbAlc, HDL-C, LDL-C, triglyceride and TC, especially in Group D. CONCLUSION: DSP might delay the occurrence and development of diabetic macro-vascular disease.