The Rayleigh law in silicon doped hafnium oxide ferroelectric thin films

A wealth of studies have confirmed that the low‐field hysteresis behaviour of ferroelectric bulk ceramics and thin films can be described using Rayleigh relations, and irreversible domain wall motion across the array of pining defects has been commonly accepted as the underlying micro‐mechanism. Recently, HfO₂ thin films incorporated with various dopants were reported to show pronounced ferroelectricity, however, their microscopic domain structure remains unclear till now. In this work, the effects of the applied electric field amplitude, frequency and temperature on the sub‐coercive polarization reversal properties were investigated for 10 nm thick Si‐doped HfO₂ thin films. The applicability of the Rayleigh law to ultra‐thin ferroelectric films was first confirmed, indicating the existence of a multi‐domain structure. Since the grain size is about 20–30 nm, a direct observation of domain walls within the grains is rather challenging and this indirect method is a feasible approach to resolve the domain structure. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Back contact–absorber interface modification by inserting carbon intermediate layer and conversion efficiency improvement in Cu2ZnSn(S,Se)4 solar cell

Carbon layers have been employed as intermediate layers between Mo back contact and Cu₂ZnSn(S_1–xSe_x)₄(CZTSSe) absorber film prepared by sol–gel and post‐selenization method. Carbon layers with appropriate thickness can significantly inhibit the formation of MoSe₂ and voids at bottom region of the absorber, and therefore reduce the series resistance remarkably. The conversion efficiency can be boosted by the introducing of the carbon layer from 6.20% to 7.24% by enhancement in short current density, fill factor and open voltage in comparison to the reference sample without carbon layer. However, excess thickness of carbon layer will worse device performance due to the deteriorated absorber crystallinity. In addition, the time‐resolved photoluminescence analysis shows that inserting the carbon layer with suitable thickness does not introduce recombination and lower minority lifetime. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

DFT study the interaction of β‐cyclodextrin with benzyl azide and phenyl acetylene in synthesis of 1,2,3‐triazoles

The phenyl acetylene and benzyl azide cycloaddition reaction in water in the presence of β‐cyclodextrin (β‐CD) as a phase transfer catalyst (PTC) can get a better yield in a shorter time. The interaction between β‐CD and phenyl acetylene or benzyl azide plays an important role in this reaction. This paper studies the complexes of β‐CD with phenyl acetylene and benzyl azide using density functional theory (DFT) method. In order to find out the orientations of guests in the cavity of β‐CD, binding energy and deformation energy are investigated, and the calculated results are confirmed by ¹H nuclear magnetic resonance (¹HNMR). The data from single point energy indicate that the inclusion complexes can improve the solubilities of phenyl acetylene and benzyl azide in water. The ¹³C and ¹⁵N spectra show that the most obvious variation concentrates on C₆ and C₈ of phenyl acetylene and N₁₅ of benzyl azide in complexes. Mulliken charge and frontier orbital are employed for revealing the charge distribution. The effect of β‐CD is discussed in terms of the calculated parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

Toxic effects of anticancer drug doxorubicin to bovine serum albumin evaluated by spectroscopic methods

The aim of this present work is to investigate the interaction between doxorubicin and bovine serum albumin (BSA) in simulated physiological conditions by spectroscopic methods to reveal potential toxic effects of the drug. The results reflected that doxorubicin made the fluorescence quenching of BSA through a static quenching procedure. The binding constants at 293, 298, and 303 K were obtained as 2.53 × 10⁵, 8.13 × 10⁴, and 3.59 × 10⁴ M^–1, respectively. There may be one binding site of doxorubicin on BSA. The thermodynamic parameters indicated that the interaction between doxorubicin and BSA was driven mainly by hydrogen bonding and electrostatic forces. Synchronous fluorescence spectra and circular dichroism (CD) results showed doxorubicin binding slightly changed the conformation of BSA with secondary structural content changes. Förster resonance energy transfer (FRET) study revealed high possibility of energy transfer with doxorubicin-Trp-212 distance of 3.48 nm. The results of the present study may provide valuable information for studying the distribution, toxicological and pharmacological mechanisms of doxorubicin in vivo.     

On the Nano/Micro-Mechanics of Metallic Glass

Metallic glass (MG) is amorphous and has some outstanding properties such as ultrahigh strength, superior elasticity, and excellent thermo-plasticity. However, as MG is relatively new to the metal family, the relationship between its physical properties and amorphous structure is still unclear. This article aims to provide an insightful discussion through a comprehensive review about the investigations in the past few decades on the scientific mechanisms of this class of material. The discussion of the paper will include the following key aspects: (1) the formation mechanism of an amorphous structure through glass transition, (2) the structural characterization and models, (3) the micromechanics of plastic event and shear band, and (4) the correlation between the amorphous structure and its mechanical properties.