scholarly journals Фотоанодирование n-Si в присутствии перекиси водорода: зависимость от напряжения

2019 ◽  
Vol 53 (1) ◽  
pp. 119
Author(s):  
Г.В. Ли ◽  
Е.В. Астрова ◽  
А.И. Лихачев
Keyword(s):  
Growth Rate ◽  
Aqueous Electrolyte ◽  
Electrochemical Etching ◽  
High Concentration ◽  
Self Organized ◽  
High Bias ◽  
Effective Valence ◽  
Dissolved Silicon ◽  
Silicon Dissolution ◽  
Etching Duration

AbstractThe fundamental aspects of the electrochemical etching of lightly doped n -Si under backside illumination conditions are studied in a solution with a low HF concentration and a high concentration of hydrogen peroxide. The data obtained are compared with those for a control electrolyte containing no H_2O_2. The morphology of the self-organized macropores, their growth rate, porosity, effective valence, and the amount of dissolved silicon are examined in relation to the applied voltage. The anodization kinetics at low and high bias voltages is analyzed. It is found that, under the same illumination, the initial photocurrent in the peroxide electrolyte is approximately twice lower than in the aqueous electrolyte, which makes it possible to state that the quantum efficiency of the photocurrent is lower. As, however, the etching duration is made longer, the current in the peroxide electrolyte strongly increases to become higher than that in the control electrolyte based on H_2O. It is found that, in the presence of H_2O_2, the depthwise growth rate of the macropores increases by more than a factor of 2, and the porosity decreases. The vertical macropore channels have a diameter smaller than that for macropores formed in the aqueous electrolyte and their walls are poorly passivated, which causes branching and the formation of secondary mesopores, the number of which grows with increasing voltage. The effective valence of silicon dissolution in the presence of H_2O_2 decreases to less than 2. The results are interpreted in terms of the Gerischer and Kolasinski models.

scholarly journals Photocatalytic Decolorization of Methyl Red on Nanoporous Anodic ZrO2 of Different Crystal Structures

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215
Author(s):  
Ewa Wierzbicka ◽  
Karolina Syrek ◽  
Klaudia Mączka ◽  
Grzegorz D. Sulka
Keyword(s):  
Photocatalytic Activity ◽  
Photocatalytic Performance ◽  
Elevated Temperatures ◽  
Aqueous Electrolyte ◽  
High Surface ◽  
High Surface Area ◽  
Methyl Red ◽  
Self Organized ◽  
Photocatalytic Decolorization ◽  
Perfect Adhesion

High surface area, self-organized nanoporous ZrO2 arrays with perfect adhesion to the Zr substrate were synthesized by anodization in an aqueous electrolyte containing (NH4)2SO4 and NH4F. The obtained semiconductor materials were tested as photocatalysts for decolorization of the methyl red (MR) as a model azo dye pollutant. It was demonstrated that as-synthesized anodic ZrO2 anodic layers are already crystalline and, therefore, do not require further thermal treatment to provide a high photocatalytic performance. However, photocatalytic efficiency could be improved by annealing at a relatively low-temperature of 350 °C. Higher annealing temperatures caused a gradual drop of photocatalytic activity. The photocatalytic behavior was correlated with the crystal phase transformation in anodic ZrO2. It was found that higher photocatalytic activity was observed for the tetragonal phase over the monoclinic phase (predominant at elevated temperatures). It results from the optimal and complex electronic structure of annealed ZrO2 with three different energy states having absorption edges at 2.0, 4.01 and 5.28 eV.

Effect of Growth Rate on Resistance ofCandida albicans Biofilms to Antifungal Agents

1998 ◽  
Vol 42 (8) ◽  
pp. 1900-1905 ◽  
Author(s):  
George S. Baillie ◽  
L. Julia Douglas
Keyword(s):  
Growth Rate ◽  
Amphotericin B ◽  
Growth Rates ◽  
Antifungal Agents ◽  
Cell Types ◽  
Planktonic Cells ◽  
High Concentration ◽  
Glucose Limitation ◽  
Daughter Cells ◽  
Cell Counts

ABSTRACT A perfused biofilm fermentor, which allows growth-rate control of adherent microbial populations, was used to assess whether the susceptibility of Candida albicans biofilms to antifungal agents is dependent on growth rate. Biofilms were generated under conditions of glucose limitation and were perfused with drugs at a high concentration (20 times the MIC). Amphotericin B produced a greater reduction in the number of daughter cells in biofilm eluates than ketoconazole, fluconazole, or flucytosine. Similar decreases in daughter cell counts were observed when biofilms growing at three different rates were perfused with amphotericin B. In a separate series of experiments, intact biofilms, resuspended biofilm cells, and newly formed daughter cells were removed from the fermentor and were exposed to a lower concentration of amphotericin B for 1 h. The susceptibility profiles over a range of growth rates were then compared with those obtained for planktonic cells grown at the same rates under glucose limitation in a chemostat. Intact biofilms were resistant to amphotericin B at all growth rates tested, whereas planktonic cells were resistant only at low growth rates (≤0.13 h−1). Cells resuspended from biofilms were less resistant than intact biofilm populations but more resistant than daughter cells; the susceptibilities of both these cell types were largely independent of growth rate. Our findings indicate that the amphotericin B resistance of C. albicans biofilms is not simply due to a low growth rate but depends on some other feature of the biofilm mode of growth.

Formation and Optical Studies of Porous GaN Thin Films via UV-Assisted Electrochemical Etching Approach

2014 ◽  
Vol 895 ◽  
pp. 45-50 ◽  
Author(s):  
Sook Fong Cheah ◽  
Sha Shiong Ng ◽  
Fong Kwong Yam ◽  
Abu Hassan Haslan ◽  
Hassan Zainuriah
Keyword(s):  
Thin Films ◽  
Potassium Hydroxide ◽  
Electrochemical Etching ◽  
Ultra Violet ◽  
Xenon Lamp ◽  
Phonon Modes ◽  
Optical Studies ◽  
Layer Characteristic ◽  
Ir And Raman ◽  
Etching Duration

This paper presents the investigation of porous gallium nitride (PGaN) thin films by ultra-violet (UV)-assisted electrochemical etching at various etching durations. The etching process was performed in potassium hydroxide aqueous solution under illumination of 150 W xenon lamp. The surface morphology and cross-section of the PGaN thin films were examined by scanning electron microscopy. Increased etching duration resulted in a more homogeneous pore distribution. Results showed that the etching duration strongly influences the layer characteristic of porous structure. Infrared (IR) and Raman studies were performed to investigate the optical properties of PGaN. IR spectroscopy revealed that the PGaN thin films exhibit distinctive IR spectra as compared to the as-grown GaN thin film. The number of interference fringes in the non-reststrahlen band is correlated to the film thickness of as-grown and PGaN thin films. The Raman measurements clearly reveal two forbidden optical phonon modes observed in all the PGaN thin films. This result indicates the crystal disordering in the films. Additionally, the findings show that the intensity of these forbidden modes becomes stronger with increasing etching duration.

Effect of Polyvinyl Pyrrolidone Molecular Weight on the Silver Morphology Synthesized by N, N-Dimethylformamide Reduction

2012 ◽  
Vol 509 ◽  
pp. 245-252 ◽  
Author(s):  
Xuan Min Zhu ◽  
Xiu Jian Zhao ◽  
Zhi Yong Ning ◽  
Xiao Tao Sui
Keyword(s):  
Molecular Weight ◽  
Growth Rate ◽  
Silver Nanoparticles ◽  
Growth Process ◽  
Selective Adsorption ◽  
The Other ◽  
Polyvinyl Pyrrolidone ◽  
Final Solution ◽  
High Concentration ◽  
Molecular Weights

Nanosized silver (Ag) was synthesized by reducing high concentration AgNO3 in N, N-dimethylformamide (DMF), in the presence of stabilizer polyvinyl pyrrolidone (PVP). PVP of two different molecular weights (MW=40000, 1300000) at the reaction temperature of 80°C and 100°C were tested for the effect on the formation of diverse silver nanoparticles. Our results indicated that the PVP with different molecular weights plays different role in the controlling of the Ag nanostructure owing to the PVP molecular selective adsorption on different crystal facets, thus affecting the growth rate of different facets of Ag nanoparticles. When all the other conditions kept the same and the temperature of 100°C, if PVP (Mw=40,000) was used, only a small amount of Ag decahedra were found. However, when the PVP with larger molecular weight such as PVP K88 (Mw=1300, 000), a large quantity of the triangular nanoprisms existed in the final solution in spite of the minority of quasi-sphere. The growth process and causation of different silver morphology with two distinct PVP have been briefly discussed.

scholarly journals Bioremediation of Phenolic Waters using the Microalgae Chlamydomonas Reinhardtii

2019 ◽  
Vol 35 (4) ◽  
pp. 1274-1278
Author(s):  
Jorge Sanchez- Aponte ◽  
Ildefonso Baldiris- Navarro ◽  
Martha Torres- Virviescas ◽  
Carlos Bohorquez
Keyword(s):  
Growth Rate ◽  
Phenolic Compounds ◽  
Chlamydomonas Reinhardtii ◽  
Future Research ◽  
High Concentration ◽  
Control Solution ◽  
Significant Difference ◽  
The Impact ◽  
Bioremediation Processes ◽  
Microalgae Growth

In this research, the capacity of biodegradation of phenolic compounds using the microalgae Chlamydomonas reinhardtii was evaluated, as well as the impact of the contaminant on the growth of the microalgae. The bioassays consisted on three phenol concentrations: 25 mgL/L, 50 mgL/L and 100 mg/L and a control solution. Bioremediation rates of approximately 99% were obtained, showing no significant difference between medium and high concentration bioassays. A good microalgae growth rate was obtained for the tests at low and medium concentration, they were above the control bioassay, but the high concentration bioassay showed an inhibition in the cell growth, this one presented growth below the control bioassay. The use of the microalgae Chlamydomonas reinhardtii in bioremediation processes of phenolic effluents, whose concentrations are below 100 mg/L, is proposed for future research.

scholarly journals Decision-Making in Physical Intelligent Systems Regulated by Growth Rate Factors

2014 ◽  
Vol 7 (4) ◽  
pp. 55
Author(s):  
Till D. Frank
Keyword(s):  
Decision Making ◽  
Growth Rate ◽  
Intelligent Systems ◽  
Equilibrium System ◽  
Discharge System ◽  
Chemical Systems ◽  
Self Organized ◽  
Current Flows ◽  
Physical And Chemical ◽  
Non Equilibrium

In the literature, self-organizing physical and chemical systems have been proposed as candidates for physical intelligent systems that may solve problems in the field of artificial intelligent in a non-algorithmic way that is not based on computation. In this theoretical study, decision-making in such physical intelligent systems is discussed in terms of non-equilibrium transitions between two self-organized states. The control parameter driving the non-equilibrium transitions is related to two growth rate factors. It is shown for a particular non-equilibrium system that the decision-making process satisfies the principle of selecting the state with the fastest growth rate factor. The system under consideration is a two component gas discharge system whose current flows can be described by means of an electronic blueprint.

Biotic and abiotic factors influencing growth rate and production of traps by the nematode-trapping fungus Duddingtonia flagrans when induced by Cooperia oncophora larvae

1999 ◽  
Vol 73 (2) ◽  
pp. 129-136 ◽  
Author(s):  
J. Grønvold ◽  
J. Wolstrup ◽  
P. Nansen ◽  
M. Larsen ◽  
S.A. Henriksen ◽  
...  
Keyword(s):  
Growth Rate ◽  
Abiotic Factors ◽  
Corn Meal ◽  
Corn Meal Agar ◽  
Duddingtonia Flagrans ◽  
Anaerobic Conditions ◽  
High Concentration ◽  
Cooperia Oncophora ◽  
Anaerobic Stress ◽  
Series Of Experiments

A series of experiments on corn meal agar was carried out to evaluate the efficacy of the nematode-trapping fungus Duddingtonia flagrans in different abiotic and biotic conditions which occur in cow pats. Above a concentration of 50 parasitic larvae (L3) cm–2 the fungus produced a maximum of between 500 and 600 nets cm–2 at 20°C in 2 days on the surface of corn meal agar. There were no differences in the trap-producing capacity of three strains of D. flagrans (CIII4, CI3 and Trol A). On agar at 30° and 20°C, the fungus responded to Cooperia oncophora L3 very quickly producing a maximum of trapping nets 1 day after induction. At 10°C, traps were produced slowly starting on day 4 after induction and continued over the following week. Duddingtonia flagrans (CI3) grew at a normal rate at least down to an oxygen concentration of 6 vol.% O2, but it did not grow anaerobically. On agar, D. flagrans (CI3) did not produce trapping nets in an anaerobic atmosphere. Moreover, C. oncophora L3 stopped migration under anaerobic conditions. When the fungal cultures were transferred to a normal aerobic atmosphere, after 1 and 2 weeks under anaerobic conditions, the C. oncophora L3 resumed migrating on the agar and, in response, D. flagrans produced traps in the same amount as when it had not been under anaerobic stress. Under microaerophilic conditions (6 vol.% O2) D. flagrans was able to grow, but the C. oncophora L3 were not able to induce trapping nets in D. flagrans (Trol A) because of larval immobility. But, as under anaerobic conditions, the fungus could return to a nematode-trapping state when transferred to a normal aerobic atmosphere within 1 or 2 weeks if migrating nematodes were present. Under natural conditions in the cow pat it is expected that the fungus will be ready to attack parasitic larvae, when the oxygen tension increases as a result of, for example the activity of the coprophilic fauna. Artificial light giving 3000–3400 Lux on the surface of the agar significantly depressed the growth rate and the production of trapping nets in D. flagrans (CI3). On agar, D. flagrans (CI3) could grow and produce trapping nets at pH levels of 6.3 to 9.3. Net-production has its optimum between pH 7 and 8. On dry faeces mycelial growth was 7–10 mm during a 15 day period while on moist faeces the fungus expanded 15–20 mm during the same period. Based on the parameters investigated, D. flagrans is expected to be especially active in the well aerated surface layer of a cow pat, an area which normally contains a high concentration of infective nematode parasite larvae, but also an area where the temperature can be high and the water content low.

Size Reduction of Silicon Nanopillars by Photo-Electrochemical Etching

2000 ◽  
Vol 638 ◽  
Author(s):  
Robert Juhasz ◽  
Jan Linnros ◽  
Pascal Kleimann
Keyword(s):  
Electron Beam Lithography ◽  
Pore Formation ◽  
Etch Rate ◽  
Electrochemical Etching ◽  
Local Scale ◽  
Size Reduction ◽  
Negative Bias ◽  
Applied Bias ◽  
High Bias ◽  
Scanning Electron

AbstractSilicon nanopillars, formed by electron beam lithography, were electrochemically etched to provide controlled size reduction. The smallest dimensions achieved were pillars of 15 nm in diameter, restricted mainly by the scanning electron microscope used for characterization. The etch rate was mainly determined by the photogeneration of carriers, by the HF concentration and by the applied voltage bias. The applied bias also controlled the resulting shape of the pillars such that a high bias resulted in etching of the pillar top whereas a negative bias caused etching only at the pillar base. For 0 V, a relatively conform etching of the pillar was observed. We discuss these phenomena in terms of electropolishing or pore formation effects on a local scale.

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