Fabrication of metallic nanopatterns with ultrasmooth surface on various substrates through lift-off and transfer process.

The smooth surface of the metallic nanostructure is essential for the propagation of surface plasmon polaritons. In this paper, we present a novel method to fabricate the metallic nanopatterns with ultra-smooth surface on various substrates. By using a silica film as the sacrificial layer, we show that the prefabricated metallic nanopatterns produced by electron beam lithography and film deposition can be hydrolyzed and transferred onto a designated substrate. The ultra-smooth surface morphology of nanopatterns has been characterized and verified by scanning electron microscopy and atomic force microscopy. More importantly, we demonstrate that this method can successfully produce a variety of nanostructures with high product yield, even onto the uneven substrate. The results indicate that our proposed method is a promising and versatile means to fabricate multiplicate smooth metallic nanostructure on various substrates for the application of nanophotonic devices.

Anabolic metabolism of autotoxic substance coumarins in plants.

Background: Autotoxicity is an intraspecific manifestation of allelopathy in plant species. The specialized metabolites and their derivatives that cause intraspecific allelopathic inhibition in the plant are known as autotoxic substances. Consequently, autotoxic substances production seriously affects the renewal and stability of ecological communities. Methods: This article systematically summarizes the types of autotoxic substances present in different plants. They mainly include phenolic compounds, terpenoids, and nitrogenous organic compounds. Phenolic coumarins are the main autotoxic substances in many plants. Therefore, we also discuss differences in coumarin types and content among plant varieties, developmental stages, and tissue parts, as well as their mechanisms of autotoxicity. In addition, we review the metabolic pathways involved in coumarin biosynthesis, the key enzymes, genes, and transcription factors, as well as factors affecting coumarin biosynthesis. Results: Coumarin biosynthesis involves three stages: (1) the formation of the coumarin nucleus; (2) acylation, hydroxylation, and cyclization; (3) structural modification. The key enzymes involved in the coumarin nuclear formation stage include PAL, C4H, 4CL, HCT, CAOMT, COSY, F6'H, and CCoAOMT1, and the key genes involved include BGA, CYP450 and MDR, among others. Ortho-hydroxylation is a key step in coumarin biosynthesis and PS, COSY and S8H are the key enzymes involved in this process. Finally, UGTs are responsible for the glycosylation modification of coumarins, and the MaUGT gene may therefore be involved in coumarin biosynthesis. Conclusion: It is important to elucidate the autotoxicity and anabolic mechanisms of coumarins to create new germplasms that produce fewer autotoxic substances.