Organic Passivation-Enhanced Ferroelectricity in Perovskite Oxide Films.

Perovskite oxides and organic-inorganic halide perovskite materials, with numerous fascinating features, have been subjected to extensive studies. Most of the properties of perovskite materials are dependence on their ferroelectricity that denoted by remanent polarization (Pr). Thus, the increase of Pr in perovskite films is mainly an effort in material physics. At present, commonplace improvement schemes, i.e., controlling material crystallinity, and post-annealing by using a high-temperature process, are normally used. However, a simpler and temporal strategy for Pr improvement is always unavailable to perovskite material researchers. In this study, an organic coating layer, low-temperature, and vacuum-free strategy is proposed to improve the Pr, directly increasing the Pr from 36 to 56 µC cm-2. Further study finds that the increased Pr originates from the suppression of the oxygen defects and Ti defects. This organic coating layer strategy for passivating the defects may open a new way for the preparation of higher-performance and cost-effective perovskite products, further improving its prospective for application in the electron devices field.

Biodegradable porous polymeric drug as a drug delivery system: alleviation of doxorubicin-induced cardiotoxicity via passive targeted release.

Doxorubicin (DOX) is an effective chemotherapeutic drug developed against a broad range of cancers, and its clinical applications are greatly restricted by the side effects of severe cardiotoxicity during tumour treatment. Herein, the DOX-loaded biodegradable porous polymeric drug, namely, Fc-Ma-DOX, which was stable in the circulation, but easy to compose in the acidic medium, was used as the drug delivery system avoiding the indiscriminate release of DOX. Fc-Ma was constructed via the copolymerization of 1,1'-ferrocenecarbaldehyde with d-mannitol (Ma) through the pH-sensitive acetal bonds. Echocardiography, biochemical parameters, pathological examination, and western blot results showed that DOX treatment caused increased myocardial injury and oxidative stress damage. In contrast, treatment with Fc-Ma-DOX significantly reduced myocardial injury and oxidative stress by DOX treatment. Notably, in the Fc-Ma-DOX treatment group, we observed a significant decrease in the uptake of DOX by H9C2 cells and a significant decrease in reactive oxygen species (ROS) production.

Giant optical absorption and ferroelectric polarization of BiCoO2S perovskite oxysulfide by first principles prediction.

Obtaining an ideal ferroelectric photovoltaic (FE-PV) material with a narrow bandgap and a large ferroelectric polarization value can enable us to achieve great practical FE-PV performance. By the introduction of sulfur into the tetragonal BiCoO3 perovskite with a C-type antiferromagnetic ordering, it is found that the bandgap of BiCoO2S decreases significantly (about 1.2 eV) while maintaining a large polarization value (about 1.86 C m-2) that is similar to the value of 1.793 C m-2 of BiCoO3. Most noteworthy is that the optical absorption of BiCoO2S is remarkably higher than those of BiCoO3 and other FE-PV materials. The decrease of the BiCoO2S bandgap originates from the movement of Co 3d states to a low-energy position due to the reduction of the Co ionicity when the less electronegative sulfur is introduced into BiCoO3 to substitute oxygen. The narrow bandgap and the high optical absorption of the BiCoO2S films grown on different substrates are favorable for FE-PV applications. In addition, the bandgap of BiCoO2S can be modulated by the doping amount of sulfur, which can help us fabricate multilayer FE-PV devices based on different bandgaps from different layers.

Self-rectifying performance in the sandwiched structure of Ag/In-Ga-Zn-O/Pt bipolar resistive switching memory.

We reported that the resistive switching of Ag/In-Ga-Zn-O/Pt cells exhibited self-rectifying performance at low-resistance state (LRS). The self-rectifying behavior with reliability was dynamic at elevated temperature from 303 to 393 K. The Schottky barrier originated from the interface between Ag electrode and In-Ga-Zn-O films, identified by replacing Ag electrode with Cu and Ti metals. The reverse current at 1.2 V of LRS is strongly suppressed and more than three orders of magnitude lower than the forward current. The Schottky barrier height was calculated as approximately 0.32 eV, and the electron injection process and resistive switching mechanism were discussed.

Temperature and pressure-mediated structural transition of ZnS nanoparticles.

We demonstrate that the structural transition of ZnS nanoparticles from sphalerite to wurtzite is influenced by high pressures and temperatures. Under the pressure of 1 GPa, the structural transition of ZnS nanoparticles commences at 250 degrees C, much lower than that 400-500 degrees C for ZnS nanoparticles under normal pressures. With the increase of the annealing temperature, the transition is enhanced then inhibited with a maximum transition fraction of 14% at 300 degrees C and disappears at 500 degrees C. At the annealing temperature of 300 degrees C, the structural transition of ZnS nanoparticles keeps almost invariable with the increase of the pressure from 0.6 GPa to 1 GPa. The mechanism for the phenomenon is discussed.

[Spectrum diagnostics for optimization of experimental parameters in thin films deposited by magnetron sputtering].

The plasma emission spectra generated during the deposition process of Si-based thin films by radio frequency (RF) magnetron sputtering using Cu and Al targets in an argon atmosphere were acquired by the plasma analysis system, which consists of a magnetron sputtering apparatus, an Omni-lambda300 series grating spectrometer, a CCD data acquisition system and an optical fiber transmission system. The variation in Cu and Al plasma emission spectra intensity depending on sputtering conditions, such as sputtering time, sputtering power, the target-to-substrate distance and deposition pressure, was studied by using the analysis lines Cu I 324. 754 nm, Cu I 327. 396 nm, Cu I 333. 784 nm, Cu I 353. 039 nm, Al I 394. 403 nm and Al I 396. 153 nm. Compared with the option of experimental parameters of thin films deposited by RF magnetron sputtering, it was shown that emission spectra analysis methods play a guiding role in optimizing the deposition conditions of thin films in RF magnetron sputtering.

Diameter- and current-density-dependent growth orientation of hexagonal CdSe nanowire arrays via electrodeposition.

Controlling the growth orientation of semiconductor nanowire arrays is of vital importance for their applications in the fields of nanodevices. In the present work, hexagonal CdSe nanowire arrays with various preferential growth orientations have been successfully yielded by employing the electrodeposition technique using porous alumina as templates (PATs). We demonstrate by experimental and theoretical efforts that the growth orientation of the CdSe nanowires can be effectively manipulated by varying either the nanopore diameter of the PATs or the deposited current density, which has significant effects on the optical properties of the CdSe nanowires. The present study provides an alternative approach to tuning the growth direction of electrodeposited nanowires and thus is of importance for the fabrication of nanodevices with controlled functional properties.

Pressure-induced transition-temperature reduction in ZnS nanoparticles.

The study of the structural transition in nanoscale materials is of particular interest for their potential applications. In the present study, we have observed a lower temperature T = 250 °C for the phase transition from the sphalerite structure to the wurtzite structure in ZnS nanoparticles under a pressure of 1 GPa, as compared to those, T = 400 and 1020 °C, for ZnS nanoparticles and bulk ZnS under normal pressure, respectively. The reduced transition temperature is attributed to the applied pressure leading to tight particle-particle contacts, which change the surface (or interfacial) environment of the nanoparticles and thus their surface (or interfacial) energy.

The control of the growth orientations of electrodeposited single-crystal nanowire arrays: a case study for hexagonal CdS.

The controllable growth of highly aligned and ordered semiconductor nanowire arrays is crucial for their potential applications in nanodevices. In the present study, both the growth orientation and the microstructure of hexagonal CdS nanowire arrays electrodeposited in a porous alumina template with 40 nm diameter pores have been controlled by simply tuning the deposition current density. An extremely low current density of 0.05 mA cm(-2) is favorable for the growth of single-crystal CdS nanowires along the normal direction of the intrinsic low-surface-energy (103) face. This can be understood well by a modified critical dimension model given in the present work.

Pressure-induced preferential growth of nanocrystals in amorphous Nd(9)Fe(85)B(6).

Control over the growth and crystallographic orientation of nanocrystals in amorphous alloys is of particular importance for the development of advanced nanocrystalline materials. In the present study, Nd(2)Fe(14)B nanocrystals with a strong crystallographic texture along the [410] direction have been produced in Nd-lean amorphous Nd(9)Fe(85)B(6) under a high pressure of 6 GPa at 923 K. This is attributed to the high pressure inducing the preferential growth of Nd(2)Fe(14)B nanocrystals in the alloy. The present study demonstrates the potential application of high-pressure technology in controlling nanocrystalline orientation in amorphous alloys.