Fabrication and Applications of Flexible Transparent Electrodes Based on Silver Nanowires

There has been an explosion of interests in using flexible transparent electrodes for next-generation flexible electronics, such as touch panels, flexible lighting, flexible solar cells, and wearable sensors. Silver nanowires (AgNWs) are a promising material for flexible transparent electrodes due to high electrical conductivity, optical transparency and mechanical flexibility. Despite many efforts in this field, the optoelectronic performance of AgNW networks is still not sufficient to replace the present material, indium tin oxide (ITO), due to the high junction resistance. Also, the environmental stability and the mechanical properties need enhancement for future commercialization. Many studies have attempted to overcome such problems by tuning the AgNW synthesis and optimizing the film-forming process. In this chapter, we survey recent progresses of AgNWs in flexible electronics by describing both fabrication and applications of flexible transparent AgNW electrodes. The synthesis of AgNWs and the fabrication of AgNW electrodes will be demonstrated, and the performance enhanced by various methods to suit different applications will be also discussed. Finally, technical challenges and future trends are presented for the application of transparent electrodes in flexible electronics

Unraveling the pH-Dependent Oxygen Reduction Performance on Single-Atom Catalysts: From Single- to Dual-Sabatier Optima

M-N-C single-atom catalysts (SACs) have emerged as a potential substitute for the costly platinum-group catalysts in oxygen reduction reaction (ORR). However, several critical aspects of M-N-C SACs in ORR remain poorly understood, including their pH-dependent activity, selectivity for 2- or 4-electron transfer pathways, and the identification of the rate-determining steps. Herein, analyzing >100 M-N-C structures and >2000 sets of energetics, we unveil for the first time a pH-dependent evolution in ORR activity volcanos from a single-peak in alkaline media to a double-peak in acids. We found that this pH-dependent behavior in M-N-C catalysts fundamentally stems from their moderate dipole moments and polarizability for O* and HOO* adsorbates, as well as unique scaling relations among ORR adsorbates. To validate our theoretical discovery, we synthesized a series of molecular M-N-C catalysts, each characterized by well-defined atomic coordination environments. Impressively, the experiments matched our theoretical predictions on kinetic current, Tafel slope, and turnover frequency in both acidic and alkaline environments. These new insights also refine the famous Sabatier principle by emphasizing the need to avoid an "acid trap" while designing M-N-C catalysts for ORR or any other pH-dependent electrochemical applications.Comment: 24 pages, 5 Figure

Periplaneta americana extract attenuates hepatic fibrosis progression by inhibiting collagen synthesis and regulating the TGF-β1/Smad signaling pathway

Introduction. Liver fibrosis is the damage repair response following chronic liver diseases. Activated hepatic stellate cells (HSCs) are the main extracellular matrix (ECM)-producing cells and key regulators in liver fibrosis. Periplaneta americana shows prominent antifibrotic effects in liver fibrosis; however, the underlying mechanisms remain undetermined. This study aimed to elucidate the therapeutic effects of P. americana extract (PA-B) on liver fibrosis based on the regulation of the TGF-β1/Smad signal pathway. Material and methods. HSCs and Sprague Dawley rats were treated with TGF-β1 and CCl4, respectively, to establish the hepatic fibrosis model in vitro and in vivo. The effect of PA-B on liver rat fibrosis was evaluated by biochemical (serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), hyaluronic acid (HA), laminin (LN), collagen type Ⅳ (Col-Ⅳ), pro-collagen type Ⅲ (PC-Ⅲ)) and histological examinations. Further, fibrogenic markers expression of alpha smooth muscle actin (α-SMA), collagen type I (Col-I), and collagen type III (Col-III), and the TGF-β1/Smad pathway-related factors were assessed by immunofluorescence (IF), real time quantitative polymerase chain reaction (RT-qPCR), and western blotting (WB). Results. Treatment of HSC-T6 cells with PA-B suppressed the expression of α-SMA, Col-I, and Col-III, downregulated the expression of TGF-β1 receptors I and II (TβR I and TβR II, respectively), Smad2, and Smad3, and upregulated Smad7 expression. PA-B mitigates pathologic changes in the rat model of liver fibrosis, thus alleviating liver index, and improving liver function and fibrosis indices. The effects of PA-B on the expression of α-SMA, Col-I, Col-III, TβR I, TβR II, Smad2, Smad3, and Smad7 were consistent with the in vitro results, including reduced TGF-β1 expression. Conclusions. The therapeutic effect of PA-B on liver fibrosis might involve suppression of the secretion and expression of TGF-β1, regulation of the TGF-β1/Smad signaling pathway, and inhibition of collagen production and secretion

Flow channel design for metallic bipolar plates in proton exchange membrane fuel cells: Experiments

This study offers an efficient design method of flow channels of metallic bipolar plates (BPPs) to improve manufacturing technique of BPPs and maximize power density in proton exchange membrane (PEM) fuel cells. Stamped thin metallic BPPs with anticorrosive and conductive coating are promising candidates for replacing conventional carbon-based BPPs. Nevertheless, unlike carbon-based BPPs, the flow channel design of metallic BPPs should take into account not only the reaction efficiency, but also formability due to the possible rupture of the metallic channel during the micro-forming process. In our previous study, a forming limit model was first proposed to predict the maximum allowable channel height by the forming process. This study is conducted to further propose the method of the design and fabrication of metallic BPPs based on the numerical model. In order to determine channel geometry design from formability perspective, response surface method is utilized to build a formability model. Combining the formability model and reaction efficiency, flow field design for metallic BPPs (channel width of 0.9 mm, rib width of 0.9 mm, channel depth of 0.4 mm and radius of 0.15 mm) is proposed. Experiments on BPP fabrication and assembled 20-cell fuel cell testing are conducted to observe forming quality of micro channel and output performance on the real fuel cell. It is shown that the stamping force grows with increasing channel depth in a nonlinear manner and a blank holder is needed to eliminate the sheet wrinkle in the forming process. The uniformity of the voltage distribution in the 1000 W-class stack further proves the reliability of metallic BPPs designed by our method. The methodology developed is beneficial to the fabrication management of metallic BPPs and effective supplement to the channel design principle for PEM fuel cells

Amorphous carbon films doped with silver and chromium to achieve ultra-low interfacial electrical resistance and long-term durability in the application of proton exchange membrane fuel cells

Amorphous carbon films doped with silver and chromium to achieve ultra-low interfacial electrical resistance and long-term durability in the application of proton exchange membrane fuel cell