Charge Transfer in Self-Assembled Fullerene-Tetraphenylporphyrin Non-Covalent Multilayer

Self-assembly of organic molecules is a promising method for generating multilayer systems for fabrication of functional devices. In particular, fullerene (C60) and porphyrin molecules offer a variety of binding modes, including π-π interactions, dipole electrostatic attraction, and hydrogen bonding, to tailor the charge separation and charge recombination limiting device performance. Here, we investigate multilayer systems obtained by the sequential physical vapor deposition of C60 and tetraphenylporphyrin (H2TPP) layers, focusing on the effect of the interfaces on the charge transfer processes. Absorbance spectra indicate noncovalent-like π-stacking, with the increment of fullerene interfaces shifting the porphyrin Soret band toward the blue. Similarly, surface photovoltage measurements in the multilayer systems show that as the number of interfaces increases, so does the photogeneration of charge. Charge separation follows carrier generation given that the recombination time, associated to trap states, decreases. This behavior indicates that the Donor-Acceptor nature of the fullerene-porphyrin bilayer system is conserved, and even enhanced, in the multilayer film, and that the number of interfaces aid to the formation of selective paths for charge carrier collection, demonstrating its potential in optoelectronic devices.

Образование и стабильность поверхностных химических соединений при взаимодействии бериллия с поверхностью (101 0) Re

It is shown that the adsorption of Be on Re (1010) in the temperature range of 850-950 K leads to the formation of specific adsorption states - surface chemical compounds (SC) of ReBe stoichiometry with a concentration of adsorbed Be atoms of ~ 1.4 • 1015 cm-2. A multilayer film of beryllium (3-4 layers) is destroyed upon heating, and at 900 K all Be atoms leave the surface into the bulk of rhenium, except those that are part of the SC; atoms from the SC, in turn, actively dissolve at T> 1050-1150 K. This corresponds to a decrease in the activation energy of dissolution upon the formation of SC from about 3.3 to 2.7 eV. Thermal desorption of beryllium takes place only at T> 2100 K due to the emergence of Be atoms dissolved in the bulk of the metal onto the surface.

Theoretical Design of a Multilayer Based Spectrally Selective Solar Absorber Applied Under Ambient Conditions

With the increasing of global energy requirements and environmental problems, the use of solar thermal energy has attracted widespread attention. The selective solar absorption coating is the most important part of a solar thermal conversion device. At present, most of the coatings work well in a vacuum at a high temperature, while not stably in the air environment. Based on the high-temperature resistant and infrared-reflective properties of ITO, a multilayer film of SiO2/Si3N4/SiO2/ITO/Cr has been designed as a selective solar absorber. The genetic algorithm is applied to optimize the material and thickness selection for each layer. The results show that the optimized multilayer film could achieve a high solar absorptance up to 90% while keeping a relatively low infrared emittance around 50% for temperature change between 600°C and 900°C. All the materials composing this film have been tested before to be chemically stable at a high temperature up to 900°C in the air environment. It is also adaptive to different incident angles from 0° to 60°. The finite-difference time-domain method was also adopted to plot the energy density distribution for different wavelengths, which provided the underlying mechanism for the selective emission spectrum. The findings in this study would provide valuable guidance to design a low-cost selective solar absorption coating without the need for vacuum generation.

Influence of gaz modified medium on the safety of flour confectionery products

С целью увеличения срока годности мучных кондитерских изделий проведены исследования влияния газовой модифицированной среды на их органолептические свойства. Изделия были упакованы в лотки из полипропилена и среднебарьерную многослойную пленку на основе полиэтилентерефталата под запайку лотков. Газовая модифицированная среда была представлена смесью углекислого газа и азота в соотношениях 20:80; 30:70; 50:50. Хранение образцов осуществлялось в течение 60 дней. Установлено, что замена воздушной среды на смесь углекислого газа и азота положительно влияла на их сохранность. Показано, что основным критерием сохранности изделий являются органолептические показатели, изменение которых происходят значительно раньше появления признаков микробиологической порчи. Использование газовой модифицированной среды при упаковывании кондитерских изделий позволило увеличить срок годности изделий в 3-6 раз. Наилучшие результаты были получены при использовании газов в соотношении 50:50. Таким образом, использование газовой модифицированной среды может рассматриваться в качестве альтернативы применению пищевых добавок для продления срока годности упакованных мучных кондитерских изделий. In order to increase the shelf life of flour confectionery products, studies have been conducted on the effect of a modified gas medium on their organoleptic properties. The products were packed in trays made of polypropylene and a medium-barrier multilayer film based on polyethylene terephthalate for sealing the trays. The gas modified medium was represented by a mixture of carbon dioxide and nitrogen in the ratios 20:80; 30:70; 50:50. The samples were stored for 60 days. It was found that the replacement of the air environment with a mixture of carbon dioxide and nitrogen positively affected their safety. It is shown that the main criterion for the safety of products are organoleptic properties, the change of which occurs much earlier than the appearance of signs of microbiological spoilage. The use of a modified gas medium in the packaging of confectionery products allowed to increase the shelf-life of products by 3-6 times. The best results were obtained when using gases in a 50:50 ratio. Thus, the application of a modified gas medium can be considered as an alternative to the use of food additives to extend the shelf-life of packaged flour confectionery products.

Multilayer Reflective Coatings for BEUV Lithography: A Review

The development of microelectronics is always driven by reducing transistor size and increasing integration, from the initial micron-scale to the current few nanometers. The photolithography technique for manufacturing the transistor needs to reduce the wavelength of the optical wave, from ultraviolet to the extreme ultraviolet radiation. One approach toward decreasing the working wavelength is using lithography based on beyond extreme ultraviolet radiation (BEUV) with a wavelength around 7 nm. The BEUV lithography relies on advanced reflective optics such as periodic multilayer film X-ray mirrors (PMMs). PMMs are artificial Bragg crystals having alternate layers of “light” and “heavy” materials. The periodicity of such a structure is relatively half of the working wavelength. Because a BEUV lithographical system contains at least 10 mirrors, the optics’ reflectivity becomes a crucial point. The increasing of a single mirror’s reflectivity by 10% will increase the system’s overall throughput six-fold. In this work, the properties and development status of PMMs, particularly for BEUV lithography, were reviewed to gain a better understanding of their advantages and limitations. Emphasis was given to materials, design concepts, structure, deposition method, and optical characteristics of these coatings.

Multilayer Reflective Coatings for BEUV Lithography: A Review

The development of microelectronics is always driven by reducing transistor size and increasing integration, from the initial micron-scale to the current few nanometers. The photolithography technique for manufacturing the transistor needs to reduce the wavelength of the optical wave, from ultraviolet, deep, to the existing extreme ultraviolet light. One approach toward decreasing the working wavelength is using lithography based on beyond extreme ultraviolet radiation (BEUV) with a wavelength around 7 nm. The BEUV lithography relies on advanced reflective optics such as periodic multilayer film X-ray mirrors (PMMs). PMMs are artificial Bragg crystals having alternate layers of “light” and “heavy” materials. The periodicity of such a structure is relatively half of the working wavelength. Since a BEUV lithographical system contains at least 10 mirrors, optics’ reflectivity becomes a crucial point. The increasing of a single mirror's reflectivity by 10% will increase the system’s overall throughput by 6 times. In this work, the properties and development status of PMMs, particularly for BEUV lithography, were reviewed to gain a better understanding of their advantages and limitations. Emphasis was given to materials, design concepts, structure, deposition method, and optical characteristics of these coatings.

Preparation and study of the physicochemical characteristics of multilayer polymer composites based on poly(ethyleneimine)-stabilized copper nanoparticles and poly(sodium 2-acrylamide-2-methyl-1-propanesulfonate)

Multilayer films were synthesized from a complex of branched polyethyleneimine (PEI) with copper nanoparticles (PEI-CuNPs) and sodium poly-2-acrylamide-2-methyl-1-propanesulfonate (PAMPSNa), applied layer-by-layer (LbL) on a solid support in an acidic medium. Protonation of the amino groups of PEI in an acidic medium increases the positive charge of the PEI-CuNPs system to +43.5 mV and promotes the formation of an interpolyelectrolyte complex between the positively charged PEI-CuNPs and the highly charged anionic polyelectrolyte PAMPS, the ζ-potential of which was -141 mV. AFM images and SEM micrographs showed a uniform distribution of spherical copper nanoparticles in the homogeneous structure of the multilayer film. The optical characteristics and hydrodynamic dimensions of PEI-CuNPs indicate the formation of PEI-CuNPs nanoparticles with sizes of 60-300 nm, with an average size of up to 100 nm. Copper nanoparticles distributed uniformly in a multilayer PEI-CuNPs/PAMPS film may be of interest for applications in the field of membrane catalysis, biochips, sensor membranes, and controlled drug delivery.