Structural and electrical properties characterization of (1–x)PbZr0.52Ti0.48O3–xBaFe0.5Nb0.5O3 system

The structural and electrical properties of (1-x)PbZr_0.52Ti_0.48O₃–xBaFe_0.5Nb_0.5O₃ ceramics system with the composition near the morphotropic phase boundary were investigated as a function of the BaFe_0.5Nb_0.5O₃ content by X-ray diffraction (XRD) and dielectric measurement technique. Studies were performed on the samples prepared by solid state reaction for x=0.1, 0.2, 0.3, 0.4 and 0.5. The XRD analysis demonstrated that with increasing BFN content in (1-x)PZT–xBFN, the structural change occurred from the tetragonal to the cubic phase at room temperature. Changes in the dielectric behavior were then related to these structural depending on the BFN content. PACS 77.84.Dy; 77.22.Ch; 77.22.Gm     

New alkylamide from the stems of Zanthoxylum nitidum

A new alkylamide, named (2E,6E,8E)-N-(2-methylpropyl)-10-oxo-2,6,8-decatrienamide (1), together with 22 known compounds (2–23), were isolated from the stems of Zanthoxylum nitidum. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR spectroscopy. The isolated compounds exhibited slightly antioxidant activities through DPPH and ABTS radical scavenging assays but showed no antibacterial activity against Streptococcus mutans ATCC2517, a dental caries causing bacteria.     

(Nitro‐κN)[2‐(phenyldiazenyl‐κN2)pyridine‐κN](2,2′:6′,2′′‐terpyridine‐κ3N)ruthenium(II) tetrafluoroborate

The Ru—N bond distances in the title complex, [Ru(NO₂)(C₁₁H₉N₃)(C₁₅H₁₁N₃)]BF₄ or [Ru(NO₂)(tpy)(azpy)]BF₄, [tpy is 2,2′:6′,2′′‐ter­pyridine and azpy is 2‐(phenyl­azo)­pyridine], are Ru—N_py 2.063 (4), Ru—N_azo 2.036 (4), Ru—N_nitro 2.066 (3) Å, and Ru—N_tpy 2.082 (4), 1.982 (3) and 2.074 (4) Å. The azo N atom is trans to the nitro group. The azo N=N bond length is 1.265 (5) Å, which is the shortest found in such complexes to date. This indicates a multiple bond between Ru and the N atom of the nitro group, and π‐­backbonding [dπ(Ru) π*(azo)] is decreased.     

Influence of B2O3 on electrical properties and phase transition of lead-free Ba(Ti0.9Sn0.1)O3 ceramics

The phase transition and electrical properties of Ba(Ti_0.9Sn_0.1)O₃ ceramics with B₂O₃ added were investigated to explore the effect of B₂O₃ addition on enhanced densification and dielectric constant of these ceramics. With increasing B₂O₃ content, a linear reduction of ferroelectric to paraelectric transition temperature was observed. In addition, higher B₂O₃ concentrations enhanced a ferroelectric relaxor behavior in the ceramics. Changes in this behavior were related to densification, second-phase formation and compositional variation of the ceramics.     

Caffeic acid and ferulic acid inhibit UVA-induced matrix metalloproteinase-1 through regulation of antioxidant defense system in keratinocyte HaCaT cells

Ultraviolet A (UVA) plays a vital role in the pathogenesis of premature skin aging through keratinocyte cytotoxicity and degradation of collagen, a main component of the extracellular matrix providing structural support. Oxidative stress caused by UVA irradiation can mediate induction of matrix metalloprotease-1 (MMP-1), a major enzyme responsible for collagen damage. Protection against UV-mediated disturbance of antioxidant defense system has been proposed as a possible mechanism by which botanical compounds slow down skin aging process. This study therefore aimed to assess inhibitory effects of caffeic acid (CA) and ferulic acid (FA), powerful plant-based phenolic antioxidants, on UVA-induced cytotoxicity and MMP-1 activity and mRNA level through modulation of antioxidant defense mechanism in immortalized human keratinocyte (HaCaT) cells. Pretreatment of the cells with CA or FA prior to UVA irradiation inhibited cytotoxicity, induction of MMP-1 activity and mRNA and oxidant formation. Moreover, CA and FA were able to up-regulate glutathione (GSH) content, γ-glutamate cysteine ligase (γ-GCL) mRNA as well as activities and mRNA expression of catalase and glutathione peroxidase (GPx) in irradiated cells. In conclusion, CA and FA provided protective effects on UVA-mediated MMP-1 induction in HaCaT cells possibly through restoration of antioxidant defense system at the cellular and molecular level.     

Impedance study of giant dielectric permittivity in BaFe0.5Nb0.5O3 perovskite ceramic

Single-phase BaFe_0.5Nb_0.5O₃ (BFN) ceramics were prepared by solid-state reaction method and were characterized by X-ray Diffraction (XRD) technique. Then, impedance spectroscopy measurements were conducted in a frequency range from 100 Hz to 1 MHz and in a temperature range from 293 to 600 K. Relaxation phenomena of non-Debye type have been observed in the BFN ceramics, as confirmed by the Cole–Cole plots. The higher values of ε′ at the lower frequencies are explained on the basis of the Maxwell–Wagner (MW) polarization model. Complex impedance analysis enables us to separate the contributions from grains and grain boundaries of our samples. We found that at higher temperatures grain boundary resistance is higher than grain resistance, irrespective of composition.     

Nanosized TiO<Subscript>2</Subscript> particles decorated on SiO<Subscript>2</Subscript> spheres (TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>): synthesis and photocatalytic activities

Nanosized TiO₂ and nano-anatase TiO₂ decorated on SiO₂ spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO₂ nano particle and TiO₂ grafted on SiO₂ sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy (TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated using methylene blue as a model pollutant. The synthesized TiO₂/SiO₂ particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO₂ particles.     

Crystal structure of bromo(2,2':6',2"-terpyridine)(2-(phenylazo)-pyridine)ruthenium(II) tetrafluoroborate.

The title compound, C26H20N6BrRu(BF4), crystallizes in the centrosymmetric space group P2(1)/n and consists of discrete complex units. The Ru(II) ion is octahedrally coordinated to one 2,2':6',2"-terpyridine (tpy), one 2-(phenylazo)pyridine (azpy) and a Br atom in trans-axial position at a distance of 2.547(5)A. The shorter Ru-N (azo) distance (1.960(3)A) than the Ru-N(py) distance (2.061(3)A) signifies a strong pi-backbonding, which leads to a longer, N=N (azo) bond (1.304(4)A).