Synthesis of One Dimensional Gold Nanostructures

Gold nanostructures with shapes of rod, dumbbells, and dog bone have been fabricated by an improved seed-mediated method. It is found that the pH change (the addition of HNO3 or HCl) and the presence of Ag+ ions have a great influence on the growth process and aspect ratios of these Au nanocrystals. UV-Vis-NIR absorption spectra for the Au colloidal show that the transverse plasmon absorption band locates at ~520 nm, while the longitudinal plasmon absorption band shifts in a wide spectra region of 750–1100 nm. The obtained Au nanostructures have been investigated by transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray diffractometer. Based on the characterizations and FDTD simulations, most of the obtained Au nanorods are single crystals, possessing an octagonal cross-section bounded by {110} and {100} faces. One model for the anisotropic growth has been proposed. It is found that slow kinetics favor the formation of single-crystalline Au nanorods

Surface Plasmon Resonance in Periodic Hexagonal Lattice Arrays of Silver Nanodisks

The surface plasmon resonance (SPR) of periodic hexagonal lattice arrays of silver nano-disks positioned on glass slides is studied using finite-difference time domain (FDTD) simulations. We investigate numerically the influence of diameter of nano-disks and the gap between nano-disks on SPR transmission spectra and electric field enhancement. We find a strong dependence of resonance wavelength on diameter of the nanodisks. With increasing the gap, electric field enhancement factor could significantly increase and reach a maximum value, which indicates that a special long-range interaction plays an important role. This study is useful for optical modulation applied in near or far field optics, sensing and data storage, and solar cell

Comparative Study on Preparation Methods for Transparent Conductive Films Based on Silver Nanowires

Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer–rod coating, spin coating, spray coating, and vacuum filtration methods, are employed to fabricate transparent conductive films based on the same silver nanowires to clarify the significance of preparation methods on the performance of the films. The surface morphology, conductive property, uniformity, and flexible stability of these four Ag NW-based films, are analyzed and compared to explore the advantages of these methods. The transparent conductive films produced by the vacuum filtration method have the most outstanding performance in terms of surface roughness and uniformity, benefitting from the stronger welding of NW-NW junctions after the press procedure. However, limited by the size of the membrane and the vacuum degree of the equipment, the small-size Ag films used in precious devices are appropriate to obtain through this method. Similarly, the spin coating method is suited to prepare Ag NWs films with small sizes, which shows excellent stability after the bending test. In comparison, much larger-size films could be obtained through Mayer-rod coating and spray coating methods. The pull-down speed and force among the Mayer-rod coating process, as well as the spray distance and traveling speed among the spray coating process, are essential to the uniformity of Ag NW films. After being treated with NaBH4 and polymethyl methacrylate (PMMA), the obtained Ag NW/PMMA films show great potential in the field of film defogging due to the Joule heating effect. Taken together, based on the advantages of each preparation method, the Ag NW-based films with desired size and performances are easier to prepare, meeting the requirements of different application fields

Surface evolution of AlGaN nanowire decorated by cesium atoms: A first principle study

Surface decoration with cesium on the photocathode is an effective method to reduce surface barriers and promote electron emission. In this study, we investigated the changes in surface properties of AlGaN nanowire coated with Cs atoms using first-principle calculations. The N bridge site is the most stable site for a single atom deposition. As more Cs atoms are deposited on the surface, the average adsorption energy increases along with the weakened ionization of Cs adatoms. The Bader charge of surface Al and Ga atoms undertake significant changes in comparison with tiny alteration of N atoms, especially for Al atom with a decrease of 0.41 |e|/atom. The variation in surface work function reaches a maximum of 2.3 ∼ 2.5 eV at Cs coverage of 0.5 ∼ 0.75 ML, which can be attributed to the synergistic effect of dipole length and charge redistribution. The donor states underneath CBM induced by the orbital overlap of Al-p, Ga-p and Cs-d electrons accompanied by the downward band bending in the band structures. This work provides theoretical insight into the surface evolution of Cs-decorated AlGaN nanowires and offers guidance for the development of state-of-the-art nanostructured vacuum devices

A Novel Discovery of Growth Process for Ag Nanowires and Plausible Mechanism

A novel growth process of silver nanowires was revealed by tracing the morphology evolution of Ag nanostructures fabricated by an improved polyol process. A mixture of Ag nanowires and nanoparticles was obtained with the usage of PVP-K25 (MW = 38,000). The products sampled at different reaction time were studied in detail using UV-visible absorption spectra and transmission electron microscopy (TEM). An interesting phenomenon unknown in the past was observed where Ag nanoparticles undergo an important dissolution-recrystallization process and Ag nanowires are formed at the expense of the preformed Ag nanoparticles. A plausible novel growth mechanism for the silver nanowires was proposed

Heat-Treatment-Induced Compositional Evolution and Magnetic State Transition in Magnetic Chalcogenide Semiconductor GeFeTe without Structural Phase Change

Control of magnetic properties in diluted magnetic semiconductors (DMSs) using external stimuli is a prerequisite for many spintronic applications. Fe-doped chalcogenide semiconductors are promising candidate materials for future spintronic devices since they offer the possibility of magnetic switching by their fast and reversible transition between amorphous and crystalline phases. However, for many proposed applications, magnetic manipulation in crystalline DMSs without a structural change is highly desirable. Thus, the ability to externally control the magnetism of magnetic chalcogenide semiconductors without structural phase change is of significance to enhance their application potential. Here we find that the annealing process could induce an antiferromagnetic (AFM)–ferromagnetic (FM) transition in magnetic chalcogenide semiconductor GeFeTe epilayers without deteriorating the crystal structure. The impact of heat treatment on magnetization in Ge_1–<i>x</i>Fe_<i>x</i>Te film depends on Fe concentration. The present data indicate that the AFM–FM transition originates from the evolution of Fe phase composition. This study gives an insight into the correlation between Fe phase composition, electronic structure, and magnetism in GeFeTe thin films

RNA Structural Dynamics Modulate EGFR-TKI Resistance Through Controlling YRDC Translation in NSCLC Cells

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) positively affect the initial control of non-small cell lung cancer (NSCLC). Rapidly acquired resistance to EGFR-TKIs is a major hurdle in successful treatment. However, the mechanisms that control the resistance of EGFR-TKIs remain largely unknown. RNA structures have widespread and crucial functions in many biological regulations; however, the functions of RNA structures in regulating cancer drug resistance remain unclear. Here, the psoralen analysis of RNA interactions and structures (PARIS) method is used to establish the higher-order RNA structure maps of EGFR-TKIs-resistant and -sensitive cells of NSCLC. Our results show that RNA structural regions are enriched in untranslated regions (UTRs) and correlate with translation efficiency (TE). Moreover, yrdC N6-threonylcarbamoyltransferase domain containing (YRDC) promotes resistance to EGFR-TKIs. RNA structure formation in YRDC 3′ UTR suppresses embryonic lethal abnormal vision-like 1 (ELAVL1) binding, leading to EGFR-TKI sensitivity by impairing YRDC translation. A potential therapeutic strategy for cancer treatment is provided using antisense oligonucleotide (ASO) to perturb the interaction between RNA and protein. Our study reveals an unprecedented mechanism through which the RNA structure switch modulates EGFR-TKI resistance by controlling YRDC mRNA translation in an ELAVL1-dependent manner

FGF19 increases mitochondrial biogenesis and fusion in chondrocytes via the AMPKα-p38/MAPK pathway

Abstract Fibroblast growth factor 19 (FGF19) is recognized to play an essential role in cartilage development and physiology, and has emerged as a potential therapeutic target for skeletal metabolic diseases. However, FGF19-mediated cellular behavior in chondrocytes remains a big challenge. In the current study, we aimed to investigate the role of FGF19 on chondrocytes by characterizing mitochondrial biogenesis and fission–fusion dynamic equilibrium and exploring the underlying mechanism. We first found that FGF19 enhanced mitochondrial biogenesis in chondrocytes with the help of β Klotho (KLB), a vital accessory protein for assisting the binding of FGF19 to its receptor, and the enhanced biogenesis accompanied with a fusion of mitochondria, reflecting in the elongation of individual mitochondria and the up-regulation of mitochondrial fusion proteins. We then revealed that FGF19-mediated mitochondrial biogenesis and fusion required the binding of FGF19 to the membrane receptor, FGFR4, and the activation of AMP-activated protein kinase alpha (AMPKα)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α)/sirtuin 1 (SIRT1) axis. Finally, we demonstrated that FGF19-mediated mitochondrial biogenesis and fusion was mainly dependent on the activation of p-p38 signaling. Inhibition of p38 signaling largely reduced the high expression of AMPKα/PGC-1α/SIRT1 axis, decreased the up-regulation of mitochondrial fusion proteins and impaired the enhancement of mitochondrial network morphology in chondrocytes induced by FGF19. Taking together, our results indicate that FGF19 could increase mitochondrial biogenesis and fusion via AMPKα-p38/MAPK signaling, which enlarge the understanding of FGF19 on chondrocyte metabolism. Video Abstrac