A new class of photo-catalytic materials and a novel principle for efficient water splitting under infrared and visible light - MgB2 as unexpected example

Water splitting is unanimously recognized as environment friendly, potentially low cost and renewable energy solution based on the future hydrogen economy. Especially appealing is photo-catalytic water splitting whereby a suitably chosen catalyst dramatically improves efficiency of the hydrogen production driven by direct sunlight and allows it to happen even at zero driving potential. Here, we suggest a new class of stable photo-catalysts and the corresponding principle for catalytic water splitting in which infrared and visible light play the main role in producing the photocurrent and hydrogen. The new class of catalysts based on ionic binary metals with layered graphite-like structures which effectively absorb visible and infrared light facilitating the reaction of water splitting, suppress the inverse reaction of ion recombination by separating ions due to internal electric fields existing near alternating layers, provide the sites for ion trapping of both polarities, and finally deliver the electrons and holes required to generate hydrogen and oxygen gases. As an example, we demonstrate conversion efficiency of 27 percent at bias voltage bias 0.5 V for magnesium di-boride working as a catalyst for photo-induced water splitting. We discuss its advantages over some existing materials and propose the underlying mechanism of photo-catalytic water splitting by binary layered metals

Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers: a thermo-magnetic Curie-switch

We investigate a novel type of interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic tri-layer through the Curie point of the weakly ferromagnetic spacer, with the exchange coupling between the strongly ferromagnetic outer layers that can be switched, on and off, or varied continuously in magnitude by controlling the temperature of the material. We use Ni-Cu alloy of varied composition as the spacer material and model the effects of proximity-induced magnetism and the interlayer exchange coupling through the spacer from first principles, taking into account not only thermal spin-disorder but also the dependence of the atomic moment of Ni on the nearest-neighbor concentration of the non-magnetic Cu. We propose and demonstrate a gradient-composition spacer, with a lower Ni-concentration at the interfaces, for greatly improved effective-exchange uniformity and significantly improved thermo-magnetic switching in the structure. The reported magnetic multilayer materials can form the base for a variety of novel magnetic devices, such as sensors, oscillators, and memory elements based on thermo-magnetic Curie-switching in the device.Comment: 15 pages, 5 figure

Singular-phase nanooptics: towards label-free single molecule detection

Non-trivial topology of phase is crucial for many important physics phenomena such as, for example, the Aharonov-Bohm effect 1 and the Berry phase 2. Light phase allows one to create "twisted" photons 3, 4 , vortex knots 5, dislocations 6 which has led to an emerging field of singular optics relying on abrupt phase changes 7. Here we demonstrate the feasibility of singular visible-light nanooptics which exploits the benefits of both plasmonic field enhancement and non-trivial topology of light phase. We show that properly designed plasmonic nanomaterials exhibit topologically protected singular phase behaviour which can be employed to radically improve sensitivity of detectors based on plasmon resonances. By using reversible hydrogenation of graphene 8 and a streptavidin-biotin test 9, we demonstrate areal mass sensitivity at a level of femto-grams per mm2 and detection of individual biomolecules, respectively. Our proof-of-concept results offer a way towards simple and scalable single-molecular label-free biosensing technologies.Comment: 19 pages, 4 figure

Topological photonics with scattering media

Scattering media, being ubiquitous in nature and critically important for assessments (e.g., biological tissues), are often considered as nuisance in optics. Here we show that it is not always the case and scattering media could be essential in providing elements of topological photonics. We demonstrate that topological darkness can be realised in the presence of scattering media due to the transverse nature of electromagnetic waves and the hairy ball theorem. We describe realizations of topological darkness in a scattering medium comprising composite gold nanostructures produced by a low-cost technique of laser structuring of thin metal films. Our results can be useful for a variety of tasks, including topological nanophotonics, optical label-free biosensing, and biomedical photonics

Non-polaritonic effects in cavity-modified photochemistry

Strong coupling of molecules to vacuum fields has been widely reported to lead to modified chemical properties such as reaction rates. However, some recent attempts to reproduce infrared strong coupling results have not been successful, suggesting that factors other than strong coupling may sometimes be involved. Here we re-examine the first of these vacuum-modified chemistry experiments, in which changes to a molecular photoisomerisation process were attributed to strong coupling of the molecules to visible light. We observed significant variations in photoisomerisation rates for molecules placed in a variety of optical cavity structures, but found no evidence that these changes need to be attributed to strong coupling. Instead, we suggest that the photoisomerisation rates involved are most strongly influenced by the absorption of ultraviolet radiation in the cavity. Our results indicate that care must be taken to rule out non-polaritonic effects before invoking strong coupling to explain any changes of chemical properties arising in cavity-based experiments.Comment: 31 pages, 16 figure

Luminescence Properties and Decay Kinetics of Mn 2+ and Eu 3+ Co-Dopant Ions in MgGa 2 O 4 Ceramics

A. Luchechko gratefully acknowledges a grant from the Institute of Physics PAS for a research visit to the institute, while A.I. Popov has been supported by project LZP-2018/1-0214 from the Latvian Council of Science.The MgGa 2 O 4 ceramics co-doped with Mn 2+ and Eu 3+ ions were synthesized via a higherature solid-state reaction technique. The samples with various Eu 3+ concentrations were characterised using high-resolution photoluminescence (PL) spectroscopy. The PL spectra show weak matrix emission in a blue spectral region with dominant excitation band around 380 nm. Manganese ions are highly excited deeply in UV region and exhibit emission band peaked at 502 nm. The Eu 3+ ions show characteristic f-f excitation and emission lines. The energy transfer between host defects and activator ions was observed. Luminescence decay curves of Mn 2+ and Eu 3+ emission showed complex kinetics with both Eu 3+ -ion concentration and excitation wavelength changes.Latvian Council of Science LZP-2018/1-0214; Latvian–Ukrainian Joint Research Project LV-UA/2016/1,M/.8-2018; project DB/RIDER0117U004443; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

ЗАСТОСУВАННЯ ВІДКРИТОГО ПРОГРАМНОГО КОМПЛЕКСУ ДЛЯ ОБРОБКИ МЕДИЧНИХ ЗОБРАЖЕНЬ MEVISLAB ПРИ ВИВЧЕННІ КУРCУ «МЕДИЧНА ІНФОРМАТИКА»

The main capabilities of the MeVisLab image analysis suite to the medical images processing are shown. The application software package structure and the user interface are described. The methodology of the MeVisLab software package usageto the studying of the corresponded topics of the Medical Informatics course is presented. An approach of the implementation of the image elements recognition algorithm is demonstrated.Показаны основные возможности программного комплекса MeVisLab в области обработки медицинских изображений. Описана его структура и интерфейс пользователя. Приведена методика применения программного комплексаMeVisLab при изучении отдельных разделов курса «Медицинская информатика». Продемонстрировано подходы к реализации алгоритмов распознавания отдельных элементов изображения.Показано основні можливості програмного комплексу MeVisLab у галузі обробки медичних зображень. Описано його структуру та інтерфейс користувача. Наведено методику застосування програмного комплексу MeVisLab при вивченні окремих розділів курсу «Медична інформатика». Продемонстровано підходи до реалізації алгоритмів розпізнавання окремих елементів зображення

ЗАСТОСУВАННЯ РЕСУРСУ WOLFRAMALPHA ДЛЯ МАТЕМАТИЧНОГО МОДЕЛЮВАННЯ ФАРМАКОКІНЕТИЧНИХ ПРОЦЕСІВ

Using information technologies in the process of teaching higher mathematics, information technologies in pharmacy helps to develop students creativethinking and better skills of work in a computer environment. It also provides the higher level of getting knowledge, helps to create and study mathematical models of different phenomena; shows how to use and research mathematical methods. The article deals with advantages and disadvantages of using WolframAlpha while  forming mathematical competence of future pharmacists.Использование современных новейших технологий в процессе преподавания курсов высшей математики, компьютерных технологий в фармации способствует формированию умений и навыков работы в условиях компьютерной среды, созданию и изучению математических моделей разнообразных явлений и процессов, демонстрации применения математических методов и их исследования. В статье рассмотрены преимущества и недостатки применения Wolframalpha в формировании предметной математической компетентности будущих фармацевтов.Використання сучасних новітніх технологій в процесі викладання вищої математики, комп'ютерних технологій уфармації сприяє формуванню вмінь та навичок роботи в умовах комп'ютерного середовища, створенню та вивченню математичних моделей різноманітних явищ та процесів, демонстрації застосування математичних методів та їх дослідження. У статті розглянуто переваги та недоліки застосування WolframAlpha у формуванні предметноїматематичної компетентності майбутніх фармацевтів