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Carbon fiber electrode has the advantages of low cost, good chemical stability, and tunable performance, which can be utilized to develop high performance marine electric field sensors. Polyaniline/carbon fiber (PANI/CF) composite electrode doped with hydrochloric acid, sulfuric acid, and phosphoric acid are respectively fabricated by electrochemical in-situ polymerization, and their electrochemical performance and electric field response of the composite electrodes are studied respectively. The results show that conductive polyaniline film is uniformly formed on the surface of carbon fiber, and the characteristic redox peak occurs in the cyclic voltammetry test. Electrochemical impedance analysis shows that the low frequency (0.01 Hz) impedance of PANI/CF composite electrode decreases to at most 1/118 of that of the blank electrode, which is conducive to the quick response to weak underwater electric field signal. In the electric field response performance test, the potential drift of hydrochloric acid doped PANI/CF composite electrode is as low as 1.77 mV/d and it can better respond to 1 mV/10 mHz low-frequency and low-intensity electric field signal. It also has the minimum linearity error (0.111%), indicating the best response sensitivity among these modified electrodes. The preparation method of the composite electrode is simple and low-cost. Therefore, it is expected to be developed into a new generation of marine electric field sensor with low cost and high performance.

The loop-mediated isothermal amplification (LAMP) primers were designed for the conserved region of the selected Nicotiana-specific gene Ntsp151 sequence, and a visual LAMP detection method for tobacco materials based on the SYBR Green I was established. The genomic DNA extraction method and reaction conditions were optimized in the detection process. Furthermore, the specificity and sensitivity of the LAMP reaction system were evaluated. The results showed that the genomic DNA extracted by Chelex-100 could be directly amplified and fluorescently colored by LAMP; the optimal reaction conditions of the LAMP primers were amplification temperature 63 °C, reaction time 60 min, Mg2+ concentration 6 mmol/L; LAMP detection method had good specificity and the results of chromogenic amplification and fluorescence detection of 17 non-tobacco materials and 1 tobacco material were consistent and had good specificity. The sensitivity test showed that the minimum detection limit of the LAMP reaction system was 102 copies/μL. The LAMP detection based on Nicotiana-specific gene Ntsp151 was result-visualized, highly sensitive, and specific, which was suitable for field inspection. [ABSTRACT FROM AUTHOR]

In order to quantitatively detect Honghuadajinyuan in mixed tobacco leaves, cultivar-specific primers and TaqMan MGB probes were designed. The specificity and sensitivity of the primers and the probes were detected, and the reaction conditions of the fluorescent quantitative PCR were determined. On this basis, a regression equation was established to quantitatively detect the single cultivar of Honghuadajinyuan in mixed tobacco leaves. The results showed that the combination of the primers and the probes H1-R/F/T had satisfactory specificity. The regression equation was established and the determination coefficient R² was 0.997. When the template DNA (55 ng·µL-1) was 2 µL, the detection limit of Honghuadajinyuan was 0.11 ng. The error range of the content of Honghuadajinyuan in mixed tobacco leaves detected by this method was between 2.5% and 3.5%, suggesting that this method could be applied to the quantitative detection of Honghuadajinyuan in specific mixed tobacco leaves. [ABSTRACT FROM AUTHOR]