Porous Silicon Photonic Crystal as a Substrate for High Efficiency Biosensing

Photonic crystals offer great possibilities for the improvement of performance of different kinds of devices. Due to the ability to control the light propagation and to change optical properties via interaction with the media photonic crystals have been widely used to increase the sensitivity of biosensing in many experimental setups. Among them some of the most interesting for practical applications are one-dimensional porous silicon photonic crystals. They could be easily fabricated, have big surface area, high sorption abilities, and have been shown to be able to change the emission of embedded luminophores. In this study we have fabricatedand performed the comprehensive investigation of the properties of hybrid system consisting of the porous silicon one-dimensional photonic crystals embedded with semiconductor quantum dots as the luminophores. We have demonstrated the ability of these systems to enhance the photoluminescence of luminophores and serve as the substrate for the high efficient biosensing. Keywords: Porous silicon, microcavity, quantum dots, luminescence enhancemen

Modeling and Optimization of the Porous Silicon Photonic Structures

Photonic crystals and optical devices based on them are of great interest nowadays and are widely used in photonics, optoelectronics, and biosensing. One of the most practically using materials to fabricate one-dimensional photonic crystal is porous silicon due to the simple fabrication process, high porosity and ability to select precisely the refractive index by controlling the porosity. It has already been shown as the suitable material to be used as an element of many photonic devices including gas sensors and biosensors. However, because of the complicated porous structure, and silicon oxidation, occurring at the atmosphere conditions, optical properties of porous silicon photonic structures need to be stabilized by preventive oxidation. In order to predict eventual optical properties of fabricated photonic structures an adequate modeling should be performed. In our study we have developed a calculation model based on the combination of effective media approximations and transfer matrix method, which could precisely predict the reflection, transmission of the porous silicon photonic structures taking into account the dispersion of the refractive index of silicon and silicon oxide, and the oxidation degree. We also used numerical finite-difference time-domain calculations in order to investigate the luminescent properties of the lumiphores embedded into the porous photonic structure. Keywords: Porous silicon, microcavity, transfer matrix, effective media, FDT

Influence of the photon - neutrino processes on magnetar cooling

The photon-neutrino processes $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$, $\gamma \to \nu \bar \nu$ and $\gamma \gamma \to \nu \bar \nu$ are investigated in the presence of a strongly magnetized and dense electron-positron plasma. The amplitudes of the reactions $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$ and $\gamma \gamma \to \nu \bar \nu$ are obtained. In the case of a cold degenerate plasma contributions of the considering processes to neutrino emissivity are calculated. It is shown that contribution of the process $\gamma \gamma \to \nu \bar \nu$ to neutrino emissivity is supressed in comparision with the contributions of the processes $\gamma e^{\pm} \to e^{\pm} \nu \bar \nu$ and $\gamma \to \nu \bar \nu$. The constraint on the magnetic field strength in the magnetar outer crust is obtained.Comment: 8 pages, LaTeX, 2 PS figures, based on the talk presented by D.A. Rumyantsev at the XV International Seminar Quarks'2008, Sergiev Posad, Moscow Region, May 23-29, 2008, to appear in the Proceeding

QCL active region overheat in pulsed mode: effects of non-equilibrium heat dissipation on laser performance

Quantum cascade lasers are of high interest in the scientific community due to unique applications utilizing the emission in mid-IR range. The possible designs of QCL are quite limited and require careful engineering to overcome some crucial disadvantages. One of them is an active region (ARn) overheat, that significantly affects the laser characteristics in the pulsed operation mode. In this work we consider the effects related to the non-equilibrium temperature distribution, when thermal resistance formalism is irrelevant. We employ the heat equation and discuss the possible limitations and structural features stemming from the chemical composition of the AR. We show that the presence of alloys in the ARn structure fundamentally limits the heat dissipation in pulsed and CW regimes due to their low thermal conductivity. Also the QCL post-growths affects the thermal properties of a device only in (near)CW mode while it is absolutely invaluable in the pulsed mod

SAMPLE TRASFORMATION AT TWO-STAGE PROBE ATOMIZATION IN GRAPHITE FURNACE FOR ATOMIC ABSORPTION SPECTROMETRY

The surface of the U-shaped tungsten probe for a graphite furnace atomic absorption analysis with two-stage probe atomization was studied using scanning electron microscopy. The aim of the work was investigation of morphology of the sample after vapor phase transfer from the tube furnace to the tungsten probe and additional thermal treatment on the probe. It is shown for the sample having complex matrix (the slurry of milled up to 80 µm gold ore) that a polycrystalline layer of agglomerated particles of size less than 1 µm is formed on the surface of the probe after primary vaporization. After additional pyrolysis on the probe at the furnace temperature1500°Cthe deposit is modified into an amorphous film and drops of reduced metals with diameter up to 1 µm. In the case of simple matrix (water solution of palladium nitrate) a solid film with clots and flakes of 50 – 100 nm micro drops of palladium is deposited on the probe. The two stage treatment leads to the simplification of chemical and phase composition of the deposit and its localization on the probe tip within2 mm. This caused substantial improvement of analytical signal associated with atomization of the deposit from the probe inserted into the graphite furnace.Keywords: atomic absorption analysis, two-stage probe atomization, graphite furnace, ore, suspension, electron microscopy.(Russian)DOI:http://dx.doi.org/10.15826/analitika.2015.19.1.008Y.А. Zakharov, D.S. Irisov1, R.R. Haibullin, I.B. Chistyakov2Kazan (Volga region) Federal University, Kazan`, Russian Federation1LLC «Atzond», Kazan`, Russian Federation2LLC «Interlab», Moscow, Russian Federatio

Free-space subcarrier wave quantum communication

We experimentally demonstrate quantum communication in 10 dB loss outdoor atmospheric channel with 5 kbit/s bitrate using subcarrier wave coding method. Free-space link was organized by telescoping system with symmetric fiber-optic collimators

Sample transformation at two-stage probe atomization in graphite furnace for atomic absorption spectrometry

С помощью растровой сканирующей электронной микроскопии исследована поверхность вольфрамового U-образного зонда, применяемого для двухстадийной зондовой атомизации проб в графитовой печи при атомно-абсорбционном анализе. Цель - проследить изменение состояния пробы после ее термической перегонки из печи на зонд и дополнительной термообработки на зонде. Показано, что в ходе первичной атомизации многокомпонентной по матричному составу пробы (суспензии размолотой до 80 мкм золотосодержащей руды), получается конденсатное отложение в виде слоя слипшихся поликристаллических частиц размером не более 1 мкм. После стадии пиролиза на зонде при температуре печи 1500⁰С это отложение превращается в оплавленную пленку с каплями восстановленных металлов диаметром до 1 мкм. В случае однокомпонентной по матричному составу пробы (водного раствора нитрата палладия) на зонде откладывается монолитная пленка со сгустками и хлопьями из микрокапель палладия размером 50-100 нм. В результате такого фракционирования химический состав пробы упрощается, а так же компактно локализуется на кончике зонда в пределах 2 мм. Это положительно сказывается на аналитическом сигнале, регистрируемом при вторичной атомизации конденсата с зонда, погружаемого в графитовую печь.The surface of the U-shaped tungsten probe for a graphite furnace atomic absorption analysis with two-stage probe atomization was studied using scanning electron microscopy. The aim of the work was investigation of morphology of the sample after vapor phase transfer from the tube furnace to the tungsten probe and additional thermal treatment on the probe. It is shown for the sample having multicomponent matrix (the slurry of milled up to 80 µm gold ore) that a polycrystalline layer of agglomerated particles of size less than 1 µm is formed on the surface of the probe after primary vaporization. After additional pyrolysis on the probe at the furnace temperature 1500 °C the deposit is modified into an amorphous film and drops of reduced metals with diameter up to 1 µm. In the case of single component matrix (water solution of palladium nitrate) a solid film with clots and flakes of 50-100 nm micro drops of palladium is deposited on the probe. The two stage treatment leads to the simplification of the sample deposit and its localization on the probe tip within 2 mm. This caused substantial improvement of analytical signal associated with atomization of the deposit from the probe inserted into the graphite furnace

Fine-tuning of Silica Coating Procedure for Preparation of Biocompatible and Bright Pbs/Sio2 Qds

Near-infrared semiconductor PbS quantum dots (QDs) with emission in biological transparency window are promising material for in vivo biolabelling and deep-tissue imaging of biological specimen. Among various approaches that render initially hydrophobic and toxic QDs biocompatible, the growth of a silica shell on the QD surface represents an efficient method to minimize QD toxicity. Nevertheless, it is important to preserve QDs emission properties after the silica coating procedure. Here we report on the optimal parameters of this procedure which allow to obtain a stable silica shell and maintain the optical properties of initial PbS QDs. Furthermore, we show that PbS QDs with the optimal SiO2 shell retain their luminescence quantum yield even after condensation into a solid film. Thus, our procedure can become a basis in development of bright, receptor-targeted NIR fluorescent probes for in vivo tumor imaging. Keywords: quantum dot, SiO2 shell, bioimagin

Suppression of hepatitis b virus by a combined activity of CRISPR/Cas9 and HBx proteins

Chronic hepatitis B is a severe liver disease associated with persistent infection with hepatitis B virus. According to recent estimations, 250 million people in the world are chronically infected, including 3 million chronically infected people in Russia. Antiviral therapeutics (nucleos(t)ide analogues and PEGylated interferon) suppress viral transcription and replication, but do not eliminate the virus from infected cells. The key reason for HBV persistency is a stable form of the viral genome (covalently closed circular DNA, cccDNA) that exists as a minichromosome protected from novel cccDNA-targeting therapeutics. Novel therapeutic approaches aimed at elimination or inactivation of cccDNA are urgently needed. CRISPR/Cas9 systems induce double strand breaks in target sites of DNA sequences. Experiments with CRISPR/Cas9 demonstrated high antiviral activity and efficient cleavage of cccDNA, but a small part of cccDNA pool remains intact. One of the main reasons of incomplete cccDNA elimination might be the structural organization of cccDNA, which persists in a heterochromatinized, very compacted form and is not be accessible to CRISPR/Cas9 systems. Viral protein HBx unwinds cccDNA and regulates cccDNA epigenetically by recruiting transcription-remodeling factors. In this work, we analyzed effects of CRISPR/Cas9 in combination with an HBxencoding plasmid or plasmids encoding mutant forms of HBx (HBxMut, which does not interact with pro-apoptotic factors Bcl-2 и Bcl-xL, and HBxNesm is localized exclusively in the nucleus and does not generate reactive oxygen species and double strand breaks in the genome). We showed that HBx improves CRISPR/Cas9 efficiency, decreasing pregenomic RNA transcription level over 98%. Moreover, we analyzed optimal ratios of plasmids encoding CRISPR/ Cas9 and HBx proteins for better antiviral efficacy. Furthermore, we discovered that HBx proteins do not have an effect on proliferation and viability of the transfected cells. In conclusion, CRISPR/Cas9 with HBx proteins exhibit high antiviral effect