Application of Two-Photon Microscopy to Study Sclerotium cepivorum Berk Sclerotia Isolated from Naturally Infested Soil and Produced In Vitro.

The danger of Sclerotium cepivorum lies in the strength of its survival structure: sclerotia. Sclerotia comprising hardened mycelium contains food reserves that allow it to remain dormant for long period, which makes the sclerotia-infested soil useless to grow any crop of the Allium species, including onion and garlic. This paper would be the first report on the application of two-photon fluorescence microscopy to the analysis of the structure of sclerotia from S. cepivorum. For this study and, in order to test the method, two different types of sclerotia were used: (1) sclerotia isolated from naturally infested soil and (2) sclerotia produced in vitro (from 20-day-old cultures). Both types of sclerotia were processed by cryopreservation and eight µm histological cuts were used to obtain an autofluorescence image. For both sclerotia, the fluorescence spectrum has three peak signals at their wall. Sclerotia from infested soil presented fluorescence peaks at 400-436, 436-475, and 515-575 nm, while signals from sclerotia produced in vitro presented fluorescence peaks at 400-442, 500-600, and 655-700 nm. Peaks at the violet electromagnetic region (400-436 and 400-442) are like that of the signals reported by the melanin. This study showed that two-photon microscopy is a novel and valuable tool for the study of sclerotia structure and their fluorescence signal, and the possibility of using it as a specific marker to direct detection in the field should be explored.

Electrical Properties of Two-Dimensional Materials Used in Gas Sensors.

In the search for gas sensing materials, two-dimensional materials offer the possibility of designing sensors capable of tuning the electronic band structure by controlling their thickness, quantity of dopants, alloying between different materials, vertical stacking, and the presence of gases. Through materials engineering it is feasible to study the electrical properties of two-dimensional materials which are directly related to their crystalline structure, first Brillouin zone, and dispersion energy, the latter estimated through the tight-binding model. A review of the electrical properties directly related to the crystalline structure of these materials is made in this article for the two-dimensional materials used in the design of gas sensors. It was found that most 2D sensing materials have a hexagonal crystalline structure, although some materials have monoclinic, orthorhombic and triclinic structures. Through the simulation of the mathematical models of the dispersion energy, two-dimensional and three-dimensional electronic band structures were predicted for graphene, hexagonal boron nitride (h-BN) and silicene, which must be known before designing a gas sensor.