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C 5 F 10 O/N 2 gas is considered to be a promising substitute for SF6 gas in medium-voltage(MV) grade electrical equipment due to its excellent environmental protection characteristics and high insulation performance. In this paper, the thermal decomposition characteristics of C 5 F 10 O/N 2 /N2 gas mixture in the temperature range of 300-500°C were studied by building a partial overheating fault experimental platform. Studies have shown that the thermal decomposition products of C 5 F 10 O/N 2 /N2 gas mixture at high temperature are C 2 F 4 , CO 2 , C 4 F 10 , C 3 F 6 , C 3 F 7 H, C 3 F 8 , CF 4 , C 2 F 6 , C 4 F 6 O 3 and C 6 F 14 . C 5 F 10 O gas decomposes at 300°C to produce a small amount of C 3 F 6 , and the temperature above 400°C will produce C 4 F 6 O 3 and C 6 F 14 . C 3 F 6 , C 4 F 6 O 3 and C 6 F 14 can be regarded as the characteristic decomposition products of the severity of partial overheating fault of C 5 F 10 O/N 2 /N 2 gas mixture. The concentration of most of the decomposition products will increase with the increase of experimental temperature, but the heating time has almost no effect on the formation of decomposition products. Relevant research results can provide guidance for the development of online monitoring equipment for partial overheating fault of C 5 F 10 O/N 2 /N2 gas mixture insulation equipment.

Herbs derived from Taraxacum genus have been used as traditional medicines and food supplements in China for hundreds of years. Taraxacum mongolicum is a famous traditional Chinese medicine derived from Taraxacum genus for the treatment of inflammatory disorders and viral infectious diseases. In the present study, the bioactive phenolic chemical profiles and antioxidant activities of flowers, leaves, and roots of Taraxacum mongolicum were investigated. Firstly, a high performance liquid chromatography method combined with segmental monitoring strategy was employed to simultaneously determine six bioactive phenolic compounds in Taraxacum mongolicum samples. Moreover, multivariate statistical analysis, including hierarchical clustering analysis, principal component analysis, and partial least squares discriminant analysis were performed to compare and discriminate different parts of Taraxacum mongolicum based on the quantitative data. The results showed that three phenolic compounds, caftaric acid, caffeic acid, and luteolin, could be regarded as chemical markers for the differences of flowers, leaves, and roots of Taraxacum mongolicum. In parallel, total phenolic contents, total flavonoid contents and antioxidant activities of different parts of Taraxacum mongolicum were also evaluated and compared. It is clear that Taraxacum mongolicum had antioxidant properties, and the antioxidant capacities of different parts of Taraxacum mongolicum in three antioxidant assays showed a similar tendency: Flowers &asymp, leaves &gt, roots, which revealed a positive relationship with their total phenolic and flavonoid contents. Furthermore, to find the potential antioxidant components of Taraxacum mongolicum, the latent relationships of the six bioactive phenolic compounds and antioxidant activities of Taraxacum mongolicum were investigated by Pearson correlation analysis. The results indicated caftaric acid and caffeic acid could be the potential antioxidant ingredients of Taraxacum mongolicum. The present work may facilitate better understanding of differences of bioactive phenolic constituents and antioxidant activities of different parts of Taraxacum mongolicum and provide useful information for utilization of this herbal medicine.

An ultrasensitive “turn off” Surface Enhanced Raman Spectroscopy (SERS) sensor was developed for the detection of heparin based on the anti-aggregation of 4-mercaptobenzoic acid stabilized gold nanoparticles. In this paper, protamine, a small protein molecule with positive charges, could induce the aggregation of 4-MBA functionalized gold nanoparticles via surface electrostatic interaction. However, in the presence of heparin, the aggregation of 4-MBA functionalized gold nanoparticles decreased due to the fact that heparin has a strong affinity toward protamine, further causing the loss of the Raman enhanced effect. The normalized SERS intensity of the Raman reporter was proportional to the concentration of added heparin and a good linear detection range was obtained from 0.05 to 20 ng mL−1 (R2 = 0.999) with a calculated detection limit of 0.03 ng mL−1. Moreover, the developed highly selective method is also successfully demonstrated in fetal bovine serum. Our method is specific, simple and cheap, which could be applied to other further research studies of heparin.

The Artemisia argyi leaf (AL) has been used as a traditional medicine and food supplement in China and other Asian countries for hundreds of years. Phytochemical studies disclosed that AL contains various bioactive constituents. Among bioactive constituents, phenolic acids have been recognized as the main active compounds in AL. To the best of our knowledge, no research has been focused on extraction method for the bioactive phenolic acids from AL. Nowadays, deep eutectic solvents (DESs) are emerging as a new type of green and sustainable solvent for efficient extraction of bioactive compounds from natural products. In the present study, an environmentally friendly extraction method based on DESs was established to extract bioactive phenolic acids from ALs. Diverse tailor-made solvents, including binary and ternary DESs, were explored for simultaneous extraction of four phenolic acids (3-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 4,5-di-O-caffeoylquinic acid) from AL. The results indicated that the ternary DES composed of a 2:1:2 molar ratio of choline chloride, malic acid, and urea showed enhanced extraction yields for phenolic acids compared with conventional organic solvents and other DESs. Subsequently, the extraction parameters for the four phenolic acids by selected tailor-made DESs, including liquid&ndash, solid ratios, water content (%) in the DESs, and extraction time, were optimized using response surface methodology and the optimal extraction conditions were: extraction time, 23.5 min, liquid&ndash, solid ratio, 57.5 mL/g (mL of DES/g dry weight of plant material), water content, 54%. The research indicated that DESs were efficient and sustainable green extraction solvents for extraction of bioactive phenolic acids from natural products. Compared to the conventional organic solvents, the DESs have a great potential as possible alternatives to those organic solvents in health-related areas such as food and pharmaceuticals.

Taxus cuspidata S. et Z. is an excellent natural source of bioactive polysaccharides and has various biological activities. The objective of this study was to evaluate the effect of antidiabetic and antitumor activities of polysaccharides from Taxus cuspidata branches and leaves (TCBL) and to determine the optimum extraction technology of TCBL using a low-temperature and high-efficiency enzyme and ultrasound-assisted coupled extraction (EUCE) method. Optimal technology parameters were determined as follows: an extraction temperature of 51 &deg, C, an extraction time of 33 min, a ratio of material to liquid of 1:19 (g:mL), and an enzyme concentration of 0.10 mg&middot, mL&minus, 1. Under the optimized conditions, the polysaccharide yield from TCBL obtained by EUCE was 4.78% &plusmn, 0.18%. The four purified polysaccharides (Pe1, Pe2, Pe3, Pe4) from TCBL are mainly composed of arabinose, galactose, glucose, a small amount of xylose, and mannose. This composition was assessed by HPIC analysis. The antidiabetic activity and antitumor activity of polysaccharides from TCBL were assayed in vitro. Among the four purified polysaccharides from TCBL, purified Pe4 had the highest inhibitory capacity against &alpha, glucosidase, and its IC50 value was 123.0 &micro, g&middot, 1. Pe1 had the highest antitumor capacity against MCF7 cells and HepG2 cells, with IC50 values of 169.0 and 132.0 &micro, 1. Pe4 had the highest antitumor effect on human cervical cancer cells (Hela), and its IC50 value was 89.9 &micro, 1. Pe4 polysaccharide demonstrated a good &alpha, glucosidase inhibitory activity and antitumor capacity against Hela cells. Therefore, Pe4 polysaccharide from TCBL is a beneficial source of potential inhibitors of type II diabetes and human cervical cancer activity.

In this study, a simple and highly sensitive colorimetric assay of H2O2 using triangular Ag nanoplates has been carried out. In the presence of H2O2, the Ag nanoplates are etched from triangle to round, which leads to the vanishment of the surface plasmon resonance (SPR) absorption at 400 nm and significant decrease the absorbance of the band at 670 nm. The color change of the reaction system from the initial blue to mauve can be observed. This proposed method can determine H2O2 with a dynamic range of 50 nM to 1 μM and a low detection limit of 1.36 nM. The high sensitivity of the triangular nanoplates can be ascribed to highly reactive edges/tips, and strongly tip sharpness and aspect ratio dependent SPR absorption of the triangular nanostructure. This sensing system is further extended to the detection of glucose by H2O2 generated from the enzymatic oxidation of glucose, and thus holds great promises in clinical applications.

In this work, hierarchical flower-like gold microstructures (HFGMs) are synthesized on a flexible PET film substrate by electrochemical deposition method as a SERS sensor without surfactant or directing agent. The effects of deposition current and electrolyte concentration on morphology and SERS performance are discussed to find the optimal preparation conditions. SERS activity of samples with different morphologies was investigated by comparing experiments and the mechanism was discussed. It shows the HFGMs with 3D nanoflakes and nanosheet tips present outstanding SERS activity with ultrasensitive detection limits. The lowest concentration of R6G that can be detected is 10−10 M, and the characteristic signals of thiram can be detected as low as 0.1 ppm. The HFGMs substrate show great potential of application in trace detection by SERS.

A novel hydrophobic-SERS substrate platform based on silver nanoparticles (AgNPs) functionalized commercially available filter paper was reported. Compared with conventional substrates, not only could this novel SERS substrate meet the requirements of simple and large-scale preparation, but also realized direct droplet-detection with reusable property. In this work, the fabrication, physical characterization, and SERS sensitivity of the substrates to spot-on food determination were studied. The experimental results show the method exhibited high reproducibility with less than 9% spot-to-spot variation in Raman intensity. Furthermore, the method was successfully applied to detect melamine in diluted milk with the instrument detection limit (IDL) down to 1 ppm in a linear correlation (1 ppm–1000 ppm). In addition, this SERS substrate could also be applied successfully in other fields, such as the determination of pesticide (thiram) and dye (malachite green) in real environment.

Flexible substrates have been proposed for daily-life applications in SERS detection due to the prominent sample collection properties such as they can be wrapped around non-planar object surface. Combining the noble metals with polymers, flexible SERS substrates could be fabricated with advantages of light weight, transparency and high SERS sensitivity. Herein, we prepare a gold nanorods (AuNRs)/poly(methyl methacrylate) (PMMA) film as flexible SERS substrate by self-assembling a uniformly AuNRs array layer on PMMA template. This AuNRs/PMMA film performs excellently on thiram trace detection with the lowest detection concentration of 0.5 ppb. The fabricated substrates were applied for practical detection with cucumber by directly covering the AuNRs/PMMA flexible film on the target surface. Furthermore, the high SERS sensitivity as well as great reproducibility present a wide range of prospections for the further application of non-plane surface.

Mercury is a major threat to the environment and to human health. It is highly desirable to develop a user-friendly kit for on-site mercury detection. Such a method must be able to detect mercury below the threshold levels (10 nM) for drinking water defined by the U.S. Environmental Protection Agency. Herein, we for the first time reported catalytically active gold amalgam-based reaction between 4-nitrophenol and NaBH4 with colorimetric sensing function. We take advantage of the correlation between the catalytic properties and the surface area of gold amalgam, which is proportional to the amount of the gold nanoparticle (AuNP)-bound Hg(2+). As the concentration of Hg(2+) increases until the saturation of Hg onto the AuNPs, the catalytic performance of the gold amalgam is much stronger due to the formation of gold amalgam and the increase of the nanoparticle surface area, leading to the decrease of the reduction time of 4-nitrophenol for the color change. This sensing system exhibits excellent selectivity and ultrahigh sensitivity up to the 1.45 nM detection limit. The practical use of this system for Hg(2+) determination in tap water samples is also demonstrated successfully.

We provide a highly sensitive and selective colorimetric assay to detect mercury ions (Hg(2+)) in aqueous environment using thiocyanuric acid (TCA) molecule-functionalized gold nanoparticles (AuNPs). This method is based on the thiophilicity of Hg(2+) and AuNPs as well as the unique optical properties of TCA-functionalized AuNPs. In the presence of TCA, AuNPs aggregate due to the strong attraction between thiol groups of TCA and surface-bounded AuCl4(-)/AuCl2(-) ions, which induces the visible color change from red to blue. With the addition of Hg(2+), Hg(2+) is more apt to interact with thiols than AuNPs. Thus, Hg(2+) can remove the AuNPs of the TCA-functionalized AuNPs and trigger AuNP aggregation redisperse again. This assay can selectively detect Hg(2+) with the detection limits as low as 0.5 nM in aqueous solution.

Here, we report a simple, sensitive and selective colorimetric method for detection of dopamine (DA) using gold nanoparticles (AuNPs). AuNPs of 15 nm size were synthesized by the citrate reduction method. The method is based on the principle that the aggregated AuNPs induced by melamine can be separated by the melamine–DA conjugate through hydrogen-bonding interactions, and thus, the blue color of AuNPs changes to blue-purple. Under optimized conditions, melamine–AuNPs are highly specific for DA and can detect melamine down to a concentration of 33 nM. Furthermore, we demonstrate the application of the approach in human urine samples, which suggests its great potential for diagnostic purposes.

The authors describe a rapid and direct SERS-based immunoassay for the determination of AFP, an important marker for diagnosis of hepatocellular carcinoma. Silver nanoparticles (AgNPs; 36 nm i.d.) serve as a support to immobilize antibody and as a SERS intensifier, and AFP-modified gold nanoparticles are employed as capturing substrate. Direct and quantitative detection of AFP is accomplished with a limit detection as low as 5 ng·mL−1. Compared to assays based on the use of metal nanoparticles, the use of gold-silver nanoparticle heterodimers as an active SERS substrate can save costs because only a single antibody is required. Moreover, the high selectivity and good linear relationship of detecting AFP in fetal bovine serum indicates its potential applicability for the direct analysis of clinical samples.

We report on a probe for the colorimetric and bare-eye detection of dopamine (DA). The optical effect is based on the finding that DA inhibits the melamine-induced aggregation of red gold nanoparticles (AuNPs) to form blue AuNP clusters. We presume that the aggregation induced by melamine is due to its strong hydrogen-bonding interactions with DA. The color changes can be monitored by spectrophotometry or the bare eye. The probes works over the 33 nM to 3.33 mM DA concentration range, and levels down to 33 nM can be quantified. The nanoprobe was successfully applied to the determination of DA in spiked serum.

Herein, we present a very simple and label-free square-wave voltammetry (SWV) aptasensor to detect potassium ions (K+), in which a K+-specific aptamer was used as an ion recognition element, and a redox couple [Fe(CN)6]3−/4− as a redox probe. At the bare gold electrode, the redox couple [Fe(CN)6]3−/4− can very easily access the electrode surface to produce a very strong SWV signal. At the K+-specific aptamer/gold electrode surface, in the presence of K+, the single-stranded DNA with guanine (G)-rich sequences could fold into a secondary structure, G-quadruplex, which resulted in less availability for a redox reaction, and led to a smaller SWV current. To improve signal intensity, gold nanoparticles (AuNPs) were anchored to a gold electrode surface which had been previously modified with self-assembled monolayers of p-aminothiophenol. The SWV peak current decreased with K+ concentration, and the plot of the SWV peak current against the logarithm of K+ concentration is linear over the range from 10 pM to 0.1 μM and 0.5 μM to 1 mM, with a detection limit of 0.13 pM. The aptasensor also showed a very good selectivity for K+ without being affected by the coexistence of other ions.

We are presenting a colorimetric assay for mercury (II) ions. It is based on citosan-functionalized gold nanoparticles (AuNPs) that act as a signaling probe. Hg (II) induces the aggregation of the chitosan-AuNPs through a chelation reaction that occurs between chitosan and Hg (II). This results in a strong decrease of the absorbance of the modified AuNPs and a color change from red to blue. This sensing system displays excellent selectivity over other metal ions and a detection limit as low as 1.35 μM which is lower than the allowed level of Hg (II) in drinking water (30 μM) as defined by World Health Organization. The method is inexpensive, facile, sensitive, and does not require the addition of other reagents in order to improving sensitivity.