Protective effects of chebulic acid from Terminalia chebula Retz. against t-BHP-induced oxidative stress by modulations of Nrf2 and its related enzymes in HepG2 cells

Food Science and Biotechnology - Although chebulic acid isolated from Terminalia chebular has diverse biological effects, its effects on the expression of nuclear factor erythroid 2-related factor...     

3D Nanoprinting of Perovskites

As competing with the established silicon technology, organic–inorganic metal halide perovskites are continually gaining ground in optoelectronics due to their excellent material properties and low‐cost production. The ability to have control over their shape, as well as composition and crystallinity, is indispensable for practical materialization. Many sophisticated nanofabrication methods have been devised to shape perovskites; however, they are still limited to in‐plane, low‐aspect‐ratio, and simple forms. This is in stark contrast with the demands of modern optoelectronics with freeform circuitry and high integration density. Here, a nanoprecision 3D printing is developed for organic–inorganic metal halide perovskites. The method is based on guiding evaporation‐induced perovskite crystallization in mid‐air using a femtoliter ink meniscus formed on a nanopipette, resulting in freestanding 3D perovskite nanostructures with a preferred crystal orientation. Stretching the ink meniscus with a pulling process enables on‐demand control of the nanostructure's diameter and hollowness, leading to an unprecedented tubular‐solid transition. With varying the pulling direction, a layer‐by‐layer stacking of perovskite nanostructures is successfully demonstrated with programmed shapes and positions, a primary step for additive manufacturing. It is expected that the method has the potential to create freeform perovskite nanostructures for customized optoelectronics.     

Composites of low bandgap conducting polymer-wrapped MWNT and poly(methyl methacrylate) for low percolation and high transparency

The composites of multi-walled carbon nanotubes (MWNT) wrapped with low bandgap conjugated polymer and poly(methyl methacrylate) (PMMA) were prepared for transparent conductive films. NIR-absorbing poly(ethyl thieno[3,4-b]thiophene-2-carboxylate) (PTTEt) with E_g of 1.0 eV was used in this study. Upon hybridization with MWNT, PTTEt in an insulating state became partially conductive due to electron transfer from PTTEt to MWNT, meaning that PTTEt can function as conductive glue interconnecting MWNT in a PMMA matrix. The electrical conduction of the composites (PTTEt-MWNT/PMMA), consisting of PTTEt-wrapped MWNT (PTTEt-MWNT/PMMA) and PMMA, showed the percolation at 0.10 wt% MWNT loading, which was ca. 0.18 wt% lower than the composites of MWNT and PMMA (MWNT/PMMA). The maximum conductivity of PTTEt-MWNT/PMMA, on the other hand, was one order of magnitude lower than that of MWNT/PMMA, suggesting that PTTEt incorporation onto MWNT for transparent conductive films is effective within a specific range of MWNT loadings (i.e., between percolation thresholds of MWNT/PMMA and PTTEt–MWNT/PMMA). The comparison of transmittance of PTTEt–MWNT/PMMA (0.18 wt% MWNT) with MWNT/PMMA (0.32 wt% MWNT), possessing the same conductivities (3 × 10^?3 S cm^?1), showed ca. 10% enhanced transmittance at 550 nm. These results imply that hybridization of low bandgap conjugated polymers with carbon nanotubes can be utilized for the reduction of percolation threshold and the increase of optical transparency without sacrificing conductivities at low MWNT loadings.     

Effects of the Domain Size on Local d33 in Tetragonal (Na0.53 K0.45Li0.02)(Nb0.8Ta0.2)O3 Ceramics

Lead‐free (Na_0.53K_0.45Li_0.02)(Nb_0.8Ta_0.2)O₃ (NKLNT) was prepared using a conventional cold‐pressing method. A commercial piezoresponse force microscope (PFM) was applied to observe the domain structures of NKLNT ceramics. The typical configuration of the ferroelectric domain was analyzed in abnormal grains with grain sizes that exceeded 40 μm, where tetragonal 90° domains are predominant. The local piezoresponse hysteresis loops were characterized and studied as a function of the domain width (dw) in the range 300–1000 nm. It was found that the amplitude signals increased and the coercive field reduced significantly with a decrease in the domain size. Finally, the local longitudinal piezoelectric coefficient (d₃₃) increased as the domain size decreased.     

Characterization of differently shaped carbon fiber composites prepared from naphtha cracking bottom oil

Different shaped carbon fibers (R-, I-, C-, Y-, and X-type) were prepared from melt-spinning of reformed naphtha cracking bottom oil precursors through various shaped spinnerets. These different shaped CFs (carbon fibers) and PVC (polyvinyl chloride) resin were compounded, and then CF/PVC composites were prepared. Precursor pitch, carbon fibers, and composites were characterized and their properties were compared. Mechanical properties of carbon fibers and composites were characterized relating to external surface area and ratio of perimeter to cross-sectional area of carbon fibers. The tensile strength of tetralobal fibers (X-type) showed five times higher than that of round-shaped fibers (R-type) due to extended external surface area. Their tensile strength of CF/PVC composite increased as ratio of perimeter to cross-sectional area of carbon fibers. The magnitude of the ratio was in order to X-, C-, I-, Y-, and R-type.     

Synthesis of vertical arrays of ultra long ZnO nanowires on noncrystalline substrates

Vertically aligned arrays of ultralong ZnO nanowires were synthesized on SiO₂ substrates with carbothermal vapor phase transport method with Au seeding layer. High density of vertically aligned ZnO nanowires with lengths from a few to ∼300 μm could be grown by controlling growth conditions. Supply of high concentration of Zn vapor and control of the ratio between Zn vapor and oxygen are found to have the most significant effects on the growth of long ZnO nanowires in the vapor-solid growth mechanism. The nanowires are of high crystalline quality as confirmed by various structural, compositional, and luminescent measurements. Luminescent and electrical properties of ZnO nanowires with different growth conditions were also investigated.     

Structural stability and sintering properties of Fe/Nb/Ti co-substituted Sr(Co0.8Fe0.1Nb0.1)1?xTixO3?δ (x?=?0.00, 0.20, 0.40) oxides

The novel Fe/Nb/Ti co-substituted Sr(Co_0.8Fe_0.1Nb_0.1)_1−x Ti _x O_3−δ (x = 0.00, 0.20, 0.40) oxides have been synthesized by the solid-state reaction method. These co-substituted strontium cobaltates possess a cubic perovskite-type structure at room temperature. Structural stability and sintering properties of the samples x = 0.00, 0.20, 0.40 were investigated by X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscopy. The combined TG and XRD results demonstrate that the structural and chemical stability of the Fe/Nb/Ti co-substituted Sr(Co_0.8Fe_0.1Nb_0.1)_1−x Ti _x O_3−δ (x = 0.20, 0.40) oxides is improved greatly compared with the sample x = 0.00 and the Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ oxide.