Diffusion doping route to plasmonic Si/SiOx nanoparticles

International audienceSemiconductor nanoparticles (SNPs) are a valuable building block for functional materials. Capabilities for engineering of electronic structure of SNPs can be further improved with development of techniques of doping by diffusion, as post-synthetic introduction of impurities does not affect the nucleation and growth of SNPs. Diffusion of dopants from an external source also potentially allows for temporal control of radial distribution of impurities. In this paper we report on the doping of Si/SiOx SNPs by annealing particles in gaseous phosphorus. The technique can provide efficient incorporation of impurities, controllable with precursor vapor pressure. HRTEM and X-ray diffraction studies confirmed that obtained particles retain their nanocrystallinity. Elemental analysis revealed doping levels up to 10%. Electrical activity of the impurity was confirmed through thermopower measurements and observation of localized surface plasmon resonance in IR spectra. The plasmonic behavior of etched particles and EDX elemental mapping suggest uniform distribution of phosphorus in the crystalline silicon cores. Impurity activation efficiencies up to 34% were achieved, which indicate high electrical activity of thermodynamically soluble phosphorus in oxide-terminated nanosilicon

Bronchial Secretory Immunoglobulin A Deficiency Correlates With Airway Inflammation and Progression of Chronic Obstructive Pulmonary Disease

Rationale: Although airway inflammation can persist for years after smoking cessation in patients with chronic obstructive pulmonary disease (COPD), the mechanisms of persistent inflammation are largely unknown

Inward and Outward FDI Country Profiles, Second Edition

This second edition contains a series of 77 standardized country profiles dealing with the inward and outward foreign direct investment (FDI) performance of 40 economies. The profiles have been peer-reviewed by a global network of experts. The publication is intended to contribute to the analysis of trends in foreign direct investment and policy issues related to them. More specifically, the individual profiles discuss FDI trends and developments (country-level developments, the corporate players); effects of the recent global crises; and the policy scene. Each profile contains a standard set of tables, including on FDI stocks and flows, sectoral and geographical FDI distributions, the largest M&As and greenfield investments, the principal foreign affiliates (for inward FDI), and the principal multinational enterprises (for outward FDI). The standardized template used to produce the profiles allows cross-country comparisons. The volume is meant to be a reference tool for anyone interested in foreign direct investment

To Break or to Brake Neuronal Network Accelerated by Ammonium Ions?

The aim of present study was to investigate the effects of ammonium ions on in vitro neuronal network activity and to search alternative methods of acute ammonia neurotoxicity prevention.Rat hippocampal neuronal and astrocytes co-cultures in vitro, fluorescent microscopy and perforated patch clamp were used to monitor the changes in intracellular Ca2+- and membrane potential produced by ammonium ions and various modulators in the cells implicated in neural networks.Low concentrations of NH4Cl (0.1-4 mM) produce short temporal effects on network activity. Application of 5-8 mM NH4Cl: invariably transforms diverse network firing regimen to identical burst patterns, characterized by substantial neuronal membrane depolarization at plateau phase of potential and high-amplitude Ca2+-oscillations; raises frequency and average for period of oscillations Ca2+-level in all cells implicated in network; results in the appearance of group of «run out» cells with high intracellular Ca2+ and steadily diminished amplitudes of oscillations; increases astrocyte Ca2+-signalling, characterized by the appearance of groups of cells with increased intracellular Ca2+-level and/or chaotic Ca2+-oscillations. Accelerated network activity may be suppressed by the blockade of NMDA or AMPA/kainate-receptors or by overactivation of AMPA/kainite-receptors. Ammonia still activate neuronal firing in the presence of GABA(A) receptors antagonist bicuculline, indicating that «disinhibition phenomenon» is not implicated in the mechanisms of networks acceleration. Network activity may also be slowed down by glycine, agonists of metabotropic inhibitory receptors, betaine, L-carnitine, L-arginine, etc.Obtained results demonstrate that ammonium ions accelerate neuronal networks firing, implicating ionotropic glutamate receptors, having preserved the activities of group of inhibitory ionotropic and metabotropic receptors. This may mean, that ammonia neurotoxicity might be prevented by the activation of various inhibitory receptors (i.e. by the reinforcement of negative feedback control), instead of application of various enzyme inhibitors and receptor antagonists (breaking of neural, metabolic and signaling systems)

Transformation of simple and complex intracellular Ca²⁺-oscillations into high-amplitude impulse-shaped Ca²⁺-oscillations by NH₄Cl or bicuculline.

<p>Neuronal cultures 12 DIV. Resting calcium level is outlined by dot-dashed lines. Calcium increment over resting level (VCi = ΔCa (a.u.)/min) is indicated on the Figures as VCi. All other abbreviations as on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g001" target="_blank">Fig 1</a>. Total number of neuronal cells in networks are: N = 116, 132, 98, 110 for Fig A, B, C and D, correspondingly. <b>(A</b>–<b>C)</b> NH₄Cl induces high-amplitude Ca²⁺-oscillations in representative cells. 200 nM of L-glutamate was added before application of NH₄Cl. <b>(C)</b> The experiment was performed in the presence of 10 μM L-NAME and 200 nM of L-glutamate. <b>(D)</b> 10 μM of bicuculline evokes high-amplitude Ca²⁺-oscillations in spontaneously firing cell. Only parts of total records are presented on Fig B and C. Initial parts were omitted for simplicity.</p

Inhibitory effect of betaine on the activation of networks by ammonium ions and its dependence on the operation of GABA(A)-receptors.

<p>Cultures 14 DIV. The records of representative cells. All other abbreviations and descriptions as on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g002" target="_blank">Fig 2</a>. <b>(A)</b> Suppression of Ca²⁺-oscillations induced by 8mM NH₄Cl after the application 10 mM of betaine. N = 136. <b>(B</b>) Disappearance of suppressive effect of betaine in the presence of GABA(A)-receptors antagonist bicuculline (10 μM). N = 124. 200 nM of L-glutamate was added before application of NH₄Cl on Fig B.</p

Ammonium chloride effects on neuronal network are concentration dependent.

<p>Here and later on calcium responses are measured by Fura-2 ratio. Records characterize individual neurons (black lines) and astrocytes (grey lines), i.e. representative cells of 90–95% cells implicated in the network. Thick horizontal black lines mark the periods of application of ammonium chloride (NH₄Cl, 0.1–4 mM), L-glutamate (200 nM) and KCl (35 mM). <b>(A)</b> Application of 0.1 mM NH₄Cl does not alter Ca²⁺ signals registered in representative cells: neurone (black line) and astrocyte (grey line). Neuronal culture 12 DIV. Number of monitored neurons in network N = 84 and number of astrocytes N₁ = 47. Here is presented one of 12 experiments (n = 12). <b>(B)</b> Application of 1 mM NH₄Cl induces one burst of high-amplitude Ca²⁺ oscillations in representative neuronal cell (black line) and does not alter significantly Ca²⁺ level in representative astrocyte (grey line). Neuronal culture 12 DIV. Number of neurons in network N = 96 and number of monitored astrocytes N₁ = 52. Here is presented 1 of 3 experiments with evoked Ca²⁺ signal. Total number of experiments n = 20. <b>(C)</b> Application of 2 mM NH₄Cl induces one burst of high-amplitude Ca²⁺ oscillations in representative neuronal cell (black line) wich is accompanied by some temporary elevation in astrocytic Ca²⁺-signal (grey line). Neuronal culture 15 DIV. Total number of neurons involved into network N = 102. Number of monitored astrocytes N₁ = 43. Here is presented 1 of 2 experiments with evoked Ca²⁺-burst. Total number of experiments n = 10. <b>(D)</b> Application of 3 mM NH₄Cl induces one burst of high-amplitude Ca²⁺ oscillations in representative neuronal cell (black line) with the rise in Ca²⁺ level in after burst period. Neuronal culture 14 DIV. Total number of neurons involved into network N = 91. Number of monitored astrocytes N₁ = 47. Here is presented 1 of 3 experiments with evoked Ca²⁺-burst. Total number of experiments n = 12. <b>(E)</b> Induction of sustained Ca²⁺-oscillations in neuronal network by 4 mM NH₄Cl. Record of representative neuron is presented. Neuronal culture 5 DIV. Total number of neurons in network N = 84. Here is presented 1 of 6 experiments with stable high-amplitude Ca²⁺-oscillations. Total number of experiments n = 10. 200 nM of L-glutamate was added before application of NH₄Cl. <b>(F)</b> The record of Ca²⁺-signalling in astrocyte evoked by 3 mM NH₄Cl. It corresponds to the experiment presented on Fig D. Application of 3 mM NH₄Cl induces immediate rise of Ca²⁺ level to new steady state in representative astrocyte (grey line). Note the significant differences in the responses of neurons (Fig B) and astrocytes to depolarizing action of 35 mM KCl. Neuronal culture 14 DIV. Total number of neurons N = 91. Number of monitored astrocytes N₁ = 47. Inserted black bars indicate the average amplitudes ± SD of intracellular Ca²⁺ level in 47 astrocytes recorded at time-points indicated. *<i>P</i><0.05 is given for difference between both values.</p

Comparative simultaneous recordings of Ca²⁺-oscillations in representative neuronal cell (A) and calcium signaling in two types of astrocytes (B) in network activated by 6 mM NH₄Cl.

<p>Neuronal culture 14 DIV. Part of the experiment presented on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g004" target="_blank">Fig 4</a>. All conditions as at <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g004" target="_blank">Fig 4</a>. <b>(A)</b> Recording of Ca²⁺ oscillations in representative neuronal cell (95% of cells) after application of NH₄Cl. This is the repeat of the recording presented on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g004" target="_blank">Fig 4A</a>. <b>(B)</b> Recordings of two types of responses of representative astrocytes are shown. NH₄Cl slightly increases astrocyte Ca²⁺_i level with generation of solitary Ca²⁺ spikes in 44 of 67 cells (black line) and induce chaotic Ca²⁺ oscillations in 23 of 67 cells (gray line).</p

Diffusion doping route to plasmonic Si/SiOx nanoparticles

International audienceSemiconductor nanoparticles (SNPs) are a valuable building block for functional materials. Capabilities for engineering of electronic structure of SNPs can be further improved with development of techniques of doping by diffusion, as post-synthetic introduction of impurities does not affect the nucleation and growth of SNPs. Diffusion of dopants from an external source also potentially allows for temporal control of radial distribution of impurities. In this paper we report on the doping of Si/SiOx SNPs by annealing particles in gaseous phosphorus. The technique can provide efficient incorporation of impurities, controllable with precursor vapor pressure. HRTEM and X-ray diffraction studies confirmed that obtained particles retain their nanocrystallinity. Elemental analysis revealed doping levels up to 10%. Electrical activity of the impurity was confirmed through thermopower measurements and observation of localized surface plasmon resonance in IR spectra. The plasmonic behavior of etched particles and EDX elemental mapping suggest uniform distribution of phosphorus in the crystalline silicon cores. Impurity activation efficiencies up to 34% were achieved, which indicate high electrical activity of thermodynamically soluble phosphorus in oxide-terminated nanosilicon

Effects of the agonists of inhibitory metabotropic receptors on the activation of neural networks by ammonium ions.

<p>Cultures 12–18 DIV. Responses of representative cells (90–95%) are presented. All other abbreviations and descriptions as on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134145#pone.0134145.g002" target="_blank">Fig 2</a>. <b>(A)</b> Suppression of Ca²⁺-oscillations induced by 8mM NH₄Cl after the application of 100 μM of metabotropic glutamate type II receptors agonist N-acetyl-aspartyl-glutamate (NAAG). 200 nM of L-glutamate was added before application of NH₄Cl. N = 97. <b>(B, C)</b> Slowing down of Ca²⁺-oscillations in the network in the presence of 8mM NH₄Cl by the agonists of α2-adrenoreceptors—UK14304 (100 nM, Fig B) and of cannabinoid CB1-receptors—mAEA (300 nM, Fig C). On Fig B the medium contained 10μM of bicuculline. N = 121 (for Fig B). N = 108 (for Fig C). Only part of total records presented on Fig C. Initial parts were omitted for simplicity.</p