Vacuum ultraviolet excitation luminescence spectroscopy of few-layered MoS 2

We report on vacuum ultraviolet (VUV) excited photoluminescence (PL) spectra emitted from a chemical vapor deposited MoS₂ few-layered film. The excitation spectrum was recorded by monitoring intensities of PL spectra at ~1.9 eV. A strong wide excitation band peaking at 7 eV was found in the excitation. The PL excitation band is most intensive at liquid helium temperature and completely quenched at 100 K. Through first-principles calculations of photoabsorption in MoS₂, the excitation was explicated and attributed to transitions of electrons from p- and d- type states in the valence band to the d- and p-type states in the conduction band. The obtained photon-in/photon-out results clarify the excitation and emission behavior of the low dimensional MoS₂ when interacting with the VUV light sources

Electrochemical reaction in single layer MoS2: nanopores opened atom by atom

Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate resolution toward DNA sequencing. Among them, molybdenum disulphide (MoS2) shows long-term stability as well as superior sensitivity enabling high throughput performance. The traditional method of fabricating nanopores with nanometer precision is based on the use of focused electron beams in transmission electron microscope (TEM). This nanopore fabrication process is time-consuming, expensive, not scalable and hard to control below 1 nm. Here, we exploited the electrochemical activity of MoS2 and developed a convenient and scalable method to controllably make nanopores in single-layer MoS2 with sub-nanometer precision using electrochemical reaction (ECR). The electrochemical reaction on the surface of single-layer MoS2 is initiated at the location of defects or single atom vacancy, followed by the successive removals of individual atoms or unit cells from single-layer MoS2 lattice and finally formation of a nanopore. Step-like features in the ionic current through the growing nanopore provide direct feedback on the nanopore size inferred from a widely used conductance vs. pore size model. Furthermore, DNA translocations can be detected in-situ when as-fabricated MoS2 nanopores are used. The atomic resolution and accessibility of this approach paves the way for mass production of nanopores in 2D membranes for potential solid-state nanopore sequencing.Comment: 13 pages, 4 figure

Large-area epitaxial monolayer MoS2

Two-dimensional semiconductors such as MoS2 are an emerging material family with wide-ranging potential applications in electronics, optoelectronics, and energy harvesting. Large-area growth methods are needed to open the way to applications. Control over lattice orientation during growth remains a challenge. This is needed to minimize or even avoid the formation of grain boundaries, detrimental to electrical, optical, and mechanical properties of MoS2 and other 2D semiconductors. Here, we report on the growth of high-quality monolayer MoS2 with control over lattice orientation. We show that the monolayer film is composed of coalescing single islands with limited numbers of lattice orientation due to an epitaxial growth mechanism. Optical absorbance spectra acquired over large areas show significant absorbance in the high-energy part of the spectrum, indicating that MoS2 could also be interesting for harvesting this region of the solar spectrum and fabrication of UV-sensitive photodetectors. Even though the interaction between the growth substrate and MoS2 is strong enough to induce lattice alignment via van der Waals interaction, we can easily transfer the grown material and fabricate devices. Local potential mapping along channels in field-effect transistors shows that the single-crystal MoS2 grains in our film are well connected, with interfaces that do not degrade the electrical conductivity. This is also confirmed by the relatively large and length-independent mobility in devices with a channel length reaching 80um

Detecting the translocation of DNA through a nanopore using graphene nanoribbons

Solid-state nanopores can act as single-molecule sensors and could potentially be used to rapidly sequence DNA molecules. However, nanopores are typically fabricated in insulating membranes that are as thick as 15 bases, which makes it difficult for the devices to read individual bases. Graphene is only 0.335 nm thick (equivalent to the spacing between two bases in a DNA chain) and could therefore provide a suitable membrane for sequencing applications. Here, we show that a solid-state nanopore can be integrated with a graphene nanoribbon transistor to create a sensor for DNA translocation. As DNA molecules move through the pore, the device can simultaneously measure drops in ionic current and changes in local voltage in the transistor, which can both be used to detect the molecules. We examine the correlation between these two signals and use the ionic current measurements as a real-time control of the graphene-based sensing device

ABOUT THE PRINCIPLES OF NEW EDITION OF THE SUBSOIL CODE OF UKRAINE

The author analyzed the main directions and principles of the new edition of the Codex of Ukraine on Subsoil and related legislative and regulatory acts, substantiated need for the introduction of the new edition of the Codex. The article shows that a number of provisions in the a new edition proposed by the Ministry of Environmental Protection, is unacceptable because it contradicts the Constitution of Ukraine. Specific proposals on the improvement of individual sections of the Codex

[Autosexing maternal form of meat-type chickens] Аутосексная материнская форма мясных кур

Бондаренко, Ю.В.; Сергеева, В.Д.; Куранова, Э.Н.; Романов, М.Н.; Красножон, С.А. Создание аутосексной материнской родительской формы мясных кур, обеспечивающей возможность разделения суточных цыплят по полу в зависимости от скорости роста зачатков маховых перьев (локус K). Опыты проведены в опытном хозяйстве им. Ф.Э. Дзержинского Крымского отделения УкрНИИП. Исходным материалом при создании аутосексной материнской формы мясных кур послужили линия Б-9 кросса Бройлер-6 и линия П-3 американского происхождения (фирма "Арбор Эйкрз"). Обе линии относятся к породе плимутрок. Типы оперяемости цыплят (локус K) определяли в течение первых суток жизни по относительной длине зачатков маховых перьев и кроющих перьев по Самсу и МакГиббону. У ранооперяющихся цыплят (ген k) зачатки маховых перьев длиннее, чем кроющих. Всего в суточном возрасте фенотипировано 35290 особей линии П-3,12793 - линии Б-9 и 1738 гибридных цыплят - Б-9 × П-3. Точность аутосексирования определяли по результатам убоя и вскрытия брюшной полости птицы в целях обследования их внутренних половых органов. Всего исследовано 458 цыплят. Разработаны следующие методические приемы выведения аутосексных комбинаций кур: выделение трех подтипов поздней оперяемости суточного молодняка, сочетание отбора цыплят по фенотипу с отбором производителей по генотипу, определение генотипа отцов по локусу K при получении племенного молодняка. Выведена аутосекская материнская форма мясных кур, обеспечивающая 97,25% точности деления гибридных цыплят по полу. Куры линии П-3 - носители генов ранней и поздней оперяемости цыплят - обладали сходными показателями продуктивности. От кур аутосексной материнской формы Б-9 × П-3 за 420 дн. жизни получено по 152 яйца на среднюю несушку. Выход цыплят на несушку составил 115 гол., что на 5,7 гол. меньше, чем у кур линии П-3. (Л. Благообразова