Silver Nanowires-Based Flexible Gold Electrode Overcoming Interior Impedance of Nanomaterial Electrodes.

In the development of nanomaterial electrodes for improved electrocatalytic activity, much attention is paid to the compositions, lattice, and surface morphologies. In this study, a new concept to enhance electrocatalytic activity is proposed by reducing impedance inside nanomaterial electrodes. Gold nanodendrites (AuNDs) are grown along silver nanowires (AgNWs) on flexible polydimethylsiloxane (PDMS) support. The AuNDs/AgNWs/PDMS electrode affords an oxidative peak current density of 50 mA cm-2 for ethanol electrooxidation, a value ≈20 times higher than those in the literature do. Electrochemical impedance spectroscopy (EIS) demonstrates the significant contribution of the AgNWs to reduce impedance. The peak current densities for ethanol electrooxidation are decreased 7.5-fold when the AgNWs are electrolytically corroded. By in situ surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) simulation, it is validated that the ethanol electrooxidation favors the production of acetic acid with undetectable CO, resulting in a more complete oxidation and long-term stability, while the AgNWs corrosion greatly decreases acetic acid production. This novel strategy for fabricating nanomaterial electrodes using AgNWs as a charge transfer conduit may stimulate insights into the design of nanomaterial electrodes.

Novel Flexible Ag/AgCl Quasi-Reference Electrode with Fishbone Nanowire Structure for Remarkable Potential Stability, Long-Term Reliability, and Noninvasive Electrocardiography.

The roadblocks for the planar silver/silver chloride (Ag/AgCl) quasi-reference electrode (qRE) development are the potential stability and long-term reliability as potentiometric sensors. Although there is a significant amount of work on potentiometric screen-printed and inkjet-printed sensors, none of the REs has comparable performance to that of the conventional glass RE and knowledge on reliable planar Ag/AgCl qREs is still limited. Here, a novel fishbone-structured flexible Ag/AgCl qRE (Fishbone-Ag/AgCl qRE) was developed and its stability and long-term reliability were significantly improved. The stability of the Fishbone-Ag/AgCl qRE was comparable to that of a commercial glass Ag/AgCl RE. In a long-term stability test, the Fishbone-Ag/AgCl qRE could continuously and stably operate for more than 4 h. Shelf-life testing revealed a 6 month life span. The conductivity and diameter of the nanowires in the fishbone structure of the Ag/AgCl qRE had important influences on electrochemical properties. The conductivity of the qRE influenced the charge-transfer rate in the electrode so that it affected the potential stability. Thicker diameter and slight chlorination on the surface of the AgNWs resulted in enhanced long-term reliability of the qRE. The capabilities of this new nanostructured material were applied in vivo for noninvasive monitoring of electrocardiogram. The discovery is elementary and substantially informs improved nanostructure RE design for testing and commercial medical device applications.

A simple and effective method for identification of Fraxini Cortex from different sources by multi-mode fingerprint combined with chemometrics.

Fraxini Cortex has a long history of being used as a medicinal plant in traditional Chinese medicine. However, it is challenging to differentiate and make quality evaluations for Fraxini Cortex from different origins due to their similarities in morphological features, as well as general chemical composition using traditional chemical analytical methods. In this study, a simple and effective method was developed to identify Fraxini Cortex from different origins by multi-mode fingerprint combined with chemometrics. Digital images of the high-performance thin-layer chromatography profiles were converted to grayscale intensity, and the common patterns of high-performance thin-layer chromatography fingerprints were generated with ChemPattern software. Authentication and quality assessment were analyzed by similarity analysis, hierarchical cluster analysis, principal component analysis, and multivariate analysis of variance. The ultra-high-performance liquid chromatography fingerprints were analyzed by similarity analysis, principal component analysis, and orthogonal partial least square-discriminant analysis. When combined with chemometrics, high-performance thin-layer chromatography and ultra-high-performance liquid chromatography fingerprint provided a simple and effective method to evaluate the comprehensive quality of Fraxini Cortex, and to distinguish its two original medicinal materials (Fraxinus chinensis Roxb. and Fraxinus rhynchophylla Hance.) recorded in the Chinese Pharmacopeia and its three adulterants (Fraxinus mandschurica Rupr., Fraxinus pennsylvanica Marsh., and Juglans mandshurica Maxim.). A similar workflow may be applied to establish a differentiation method for other medicinal and economic plants.

Profiling and identification of aqueous extract of Cordyceps sinensis by ultra-high performance liquid chromatography tandem quadrupole-orbitrap mass spectrometry.

Characterization of aqueous extract in traditional Chinese medicine (TCM) is challenging due to the poor retention of the analytes on conventional C18 columns. This study presents a systematic characterization method based on a rapid chromatographic separation (8 min) on a polar-modified C18 (Waters Cortecs T3) column of aqueous extract of Cordyceps sinensis. UHPLC-HRMS method was used to profile components in both untargeted and targeted manners by full MS/PIL/dd-MS2 acquisition approach. The components were identified or tentatively identified by reference standards comparison, fragmentation rules elucidation and available databases search. A total of 91 components, including 10 nucleobases, 20 nucleosides, 39 dipeptides, 18 amino acids and derivatives and 4 other components, were characterized from the aqueous extract of C. sinensis. And this was the first time to systematically report the presence of nucleosides and dipeptides in C. sinensis, especially for modified nucleosides. The chemical basis inquiry of this work would be beneficial to mechanism exploration and quality control of C. sinensis and related products. Meanwhile, this work also provided an effective solution for characterization of aqueous extract in TCM.