Littérature scientifique sur le sujet « Lifetimes intercalation »

The subject of investigation was porous glass produced using a sol-gel technique. ortho-Ps lifetimes and intensities in the material were determined as a function of temperature and pressure. Temperature was ranged from 100 to 500 K while the pressure from 0 to 1200 MPa. Nitrogen gas intercalation into pore structure was observed up to 100 MPa.

The catalytic activity of 1,8-diazabicyclo [5,4,0]undec-7-ene-intercalated α-zirconium phosphates (α-ZrP·DBU) as thermal latent catalysts in the reaction of hexamethylene diisocyanate (HDI) and phenol was investigated. α-ZrP intercalation compounds with varying amounts of DBU (α-ZrP·xDBU, where x = 0.58, 0.44, 0.22, and 0.10) were prepared. The reaction of HDI and phenol with α-ZrP·DBU was carried out at varying temperatures for 30 min periods. The α-ZrP·DBU showed high catalytic activity in the reaction of HDI-phenol under heating conditions. The α-ZrP·DBU extended the pot lifetimes at 25 °C.

Relative values have been obtained for the cross section of fluorescence of tetrakis(4-N-methylpyridyl)porphine and the zinc(II) complex with DNA. Time-resolved fluorescence spectra have been used to assign fluorescence of porphyrins which intercalate at or are externally bound to DNA. The experimental data suggest that an equilibrium distribution for intercalated and externally groove-bound to DNA of porphyrin is reached for [Formula: see text] complexes. Radiative lifetimes of the various porphyrin species have been determined and evidence is found suggesting the contribution of non-linear effects to the intensity of laser induced fluorescence of r > 1000 complexes. Key words: cross section, fluorescence, porphyrin–DNA complexes, intercalation, outside bound.

In this work, organic–inorganic hybrid ultrathin transparent films (UTFs), produced by layer-by-layer (LBL) assembly of the europium inclusion complex of [Formula: see text]-cyclodextrin ([Formula: see text]-CD) and Mg–Al-layered double hydroxide (MgAl–NO3–LDHs) nanosheets, are reported. UV-visible (UV-Vis) absorption and fluorescence spectroscopy show orderly growth of the europium inclusion complex of [Formula: see text]-CD/layered double hydroxide (EICC/LDH) films with an increasing number of deposition cycles. X-ray diffraction and scanning electron microscopy measurements indicate that the films feature periodic layered structures with uniform surface morphology. Moreover, when EICC is assembled with inorganic rigid LDH nanosheets, the lifetimes are prolonged due to the isolation effect, and the UTFs are transparent with high brightness, which indicate that these films could serve as new optical materials.

Results of in situ optical (reflectance, Raman scattering) and 00l x-ray diffraction studies of hydrogen chemisorption in Grafoil-based stage 1 C8K intercalation compounds are presented. Upon hydrogen uptake, stage 2 KC8H2/3 was found to coexist with C8K forming first in the optical skin depth. The intensities of the 00l x-ray diffraction peaks show quantitatively that the reaction C8K + 1/2xH2 ⇉ (1 − 3/2x)C8K + 3/2xC8KH2/3 occurs for x>0.4 in the bulk. The effects of the surface morphology of Grafoil on the near-normal incidence reflectance was investigated and found to be described by an energy (E) dependent function S(E) = exp[−aEn], such that the corrected spectrum Rc = SR, where R is the Grafoil reflectance. In this manner, reflectance spectra of C8K-Grafoil and C8KH2/3-Grafoil were quantitatively analyzed to determine the free carrier contribution. The free carrier lifetimes were found to be a factor of 2 shorter in Grafoil-based hosts, compared to highly oriented pyrolytic graphite-based hosts. The optical results for C8KH2/3 indicate the H(ls) band is full (or very nearly full).

Artificial membranes are models for biological systems and are important for applications. We introduce a dry two-step self-assembly method consisting of the high-vacuum evaporation of phospholipid molecules over silicon, followed by a subsequent annealing step in air. We evaporate dipalmitoylphosphatidylcholine (DPPC) molecules over bare silicon without the use of polymer cushions or solvents. High-resolution ellipsometry and AFM temperature-dependent measurements are performed in air to detect the characteristic phase transitions of DPPC bilayers. Complementary AFM force-spectroscopy breakthrough events are induced to detect single- and multi-bilayer formation. These combined experimental methods confirm the formation of stable non-hydrated supported lipid bilayers with phase transitions gel to ripple at 311.5 ± 0.9 K, ripple to liquid crystalline at 323.8 ± 2.5 K and liquid crystalline to fluid disordered at 330.4 ± 0.9 K, consistent with such structures reported in wet environments. We find that the AFM tip induces a restructuring or intercalation of the bilayer that is strongly related to the applied tip-force. These dry supported lipid bilayers show long-term stability. These findings are relevant for the development of functional biointerfaces, specifically for fabrication of biosensors and membrane protein platforms. The observed stability is relevant in the context of lifetimes of systems protected by bilayers in dry environments.

Photophysical properties of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin ( TMpyP 4) and its metallocomplexes M (II) TMpy P4 ( M = Zn , Cu , Ni , Co ) bound to natural DNA and synthetic poly-, oligo- and mononucleotides are considered with a primary emphasis placed upon intermolecular interaction of the photoexcited porphyrins with the nearest environment. Quenching of the fluorescent S 1 (but not triplet T 1) state due to guanine to porphyrin electron transfer is observed for TMpyP 4 intercalated between GC base pairs of the double-strand helixes, whereas in the case of TMpyP 4 complexed with guanosine monophosphate (GMP) both S 1 and T 1 states of the porphyrin are quenched. Furthermore, a dependence of the efficiency of TMpyP 4 triplet state quenching by the dissolved molecular oxygen from air on the porphyrin localization enables one to readily distinguish porphyrin groove binding mode from intercalation. Excited states of the TMpyP 4 complexes with transition metals, in spite of their very short lifetimes, also interact with nucleic acid components by means of an axial ligand binding/release to/from the metal. A possible structure of the five-coordinate excited complex (“exciplex”) formed in case of CuTMpyP 4 groove binding to some single- and double-strand polynucleotides is discussed.

Lithium metal anodes offer the possibility of a ten-fold increase in capacity versus standard intercalation anodes such as graphite. However, to date, there has been limited success using commercially available liquid electrolytes for batteries with lithium metal anodes. A critical issue in LiPF6 carbonate electrolytes results from the reaction of trace water (<100 ppm) with PF5, which is in equilibrium with the PF6 - anion, to produce hydrofluoric acid (HF) and difluorophosphoric acid. These reaction products contribute to lithium passivation, transition-metal leaching and subsequent particle cracking at the cathode, and degradation of cell components. Furthermore, HF begins an autocatalytic degradation cycle, so if not removed, can continually decompose the carbonate solvents in a self-sustaining cycle. Here, we demonstrate the effectiveness of a simple and scalable modification procedure of 1M LiPF6 ethylene carbonate (EC)/diethylcarbonate (DEC) (50/50 v/v) electrolyte to greatly enhance performance of lithium-metal batteries. Phosphorus pentoxide (P2O5) added to commercial, battery-grade electrolyte performs the dual functions of both scavenging HF and H2O, while also generating chemical species that promote formation of a beneficial, POxFy-rich SEI layer upon cycling. In commercial-scale pouch cells (0.4 Ah), performance using the modified electrolyte is vastly superior, with 87.7% capacity retention at >230 cycles and minimal hysteresis, to that of the cell with as-received electrolyte, which failed after approximately 30 cycles. Electrodes harvested after 30 cycles in the commercial electrolyte yielded cracked cathode particles and transition metal migration to the anode surface, while these were not seen with the modified electrolyte, corroborating the performance enhancement resulting from HF scavenging. Rigorously quantitative, liquid-state 19F, 31P, 1H, and 13C NMR of the modified electrolyte proves complete removal of residual HF in addition to revealing a plethora of new fluorophosphate species, while two-dimensional 19F{31P} correlation experiments were used to confidently establish signal assignments. These fluorophosphate moieties make up the anodic surface layer that promotes smooth and uniform lithium electrodeposition, further enhancing performance. Understanding the relationship between electrolyte speciation and electrochemical performance is crucial for careful design of electrolyte additives, and in particular, multi-functional materials such as P2O5 offer simple but highly effective improvements to resultant electrolyte formulations. Overall, we achieve enhanced operation of lithium-metal batteries using a P2O5-modified LiPF6 carbonate electrolyte as a result of HF and H2O removal, alongside formation of favorable SEI-forming species. Through NMR, we quantitatively established speciation of this electrolyte to better understand the improved performance and elucidate the major reaction pathways. Reference: Zhang, J., et al. Performance Leap of Lithium Metal Batteries in LiPF6 Carbonate Electrolyte by a Phosphorus Pentoxide Scavenger. (Under review, 2022)

Prussian blue analogs, e.g., nickel hexacyanoferrate, NiFe(CN)6 or NiHCF, are promising candidates as low-cost and high-rate intercalation materials for secondary batteries.1–4 Recently, this material class has been shown to possess tremendous potential for a novel energy-efficient water desalination approach.5–8 Rising water demands are exacerbating water scarcity in many world regions. It is estimated that 60% of the global population will face severe water scarcity by 2025.9 The growing water demand necessitates new desalination technologies with high energy efficiency, low capital and operating cost and high freshwater output. In this work, we assess the performance and lifetime of electrochemical water desalination cells based on sodium intercalation into nickel hexacyanoferrate.10–12 The battery desalination cells feature a symmetric design, with two NiHCF electrodes at opposite state-of-charge (SOC), capable of intercalating Na+-ions into their crystal structure. The electrodes are separated by an anion exchange membrane, a porous functionalized polyether ether ketone (PEEK) membrane, that only permits negatively charged ions, e.g., Cl--ions, to pass. Two feed water streams with 20 mM NaCl enter the symmetric cell on either side (see Figure 1a). During charge of the symmetric cell, incoming Na+-ions are removed from one water stream and intercalated into the NiHCF electrode at low SOC. Simultaneously, Na+-ions are deintercalated from the opposite NiHCF electrode at high SOC. In order to maintain charge neutrality, Cl--ions cross the anion exchange membrane. Thus, during every charge/discharge cycle, one water stream is desalinated forming a freshwater stream, while the other is enriched in NaCl forming a brine waste stream (see Figure 1b). In order to quantify performance and lifetime of the novel battery-type water desalination cells, we define and measure objective metrics. We see that energy consumption (Wh/l) and productivity (l/h/m2) of NiHCF/NiHCF cells are superior to cells based on membrane capacity deionization (mCDI). Stable charge/discharge cycling of NiHCF/NiHCF cells can be achieved for over 500 cycles with NaCl feed water, but rapid aging is observed with CaCl2 feeds. Synchrotron-based characterization of NiHCF/NiHCF cells is used to elucidate the reason for capacity fade. X-ray absorption spectroscopy and X-ray fluorescence spectroscopy reveal Fe dissolution from the NiHCF active material as a primary aging mode with CaCl2 water feeds. References Wessells, C. D., Peddada, S. V., Huggins, R. A. & Cui, Y. Nickel hexacyanoferrate nanoparticle electrodes for aqueous sodium and potassium ion batteries. Nano Lett. 11, 5421–5425 (2011). Wessells, C. D. et al. Tunable reaction potentials in open framework nanoparticle battery electrodes for grid-scale energy storage. ACS Nano 6, 1688–1694 (2012). Pasta, M. et al. Full open-framework batteries for stationary energy storage. Nat. Commun. 5, 1–9 (2014). Firouzi, A. et al. Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries. Nat. Commun. 9, (2018). Pasta, M., Wessells, C. D., Cui, Y. & La Mantia, F. A desalination battery. Nano Lett. 12, 839–843 (2012). Lee, J., Kim, S. & Yoon, J. Rocking Chair Desalination Battery Based on Prussian Blue Electrodes. ACS Omega 2, 1653–1659 (2017). Kim, T., Gorski, C. A. & Logan, B. E. Low Energy Desalination Using Battery Electrode Deionization. Environ. Sci. Technol. Lett. 4, 444–449 (2017). Porada, S., Shrivastava, A., Bukowska, P., Biesheuvel, P. M. & Smith, K. C. Nickel Hexacyanoferrate Electrodes for Continuous Cation Intercalation Desalination of Brackish Water. Electrochim. Acta 255, 369–378 (2017). Jones, E., Qadir, M., van Vliet, M. T. H., Smakhtin, V. & Kang, S. mu. The state of desalination and brine production: A global outlook. Sci. Total Environ. 657, 1343–1356 (2019). Metzger, M. et al. Techno-economic analysis of capacitive and intercalative water deionization. Energy Environ. Sci. 13, 1544–1560 (2020). Sebti, E. et al. Removal of Na+ and Ca2+ with Prussian blue analogue electrodes for brackish water desalination. Desalination 487, (2020). Besli, M. M. et al. Performance and lifetime of intercalative water deionization cells for mono- and divalent ion removal. Desalination 517, 115218 (2021). Figure 1. (a) Battery-type water desalination approach in symmetric NiHCF/NiHCF cells with two salt water streams entering the cell and a brine stream and freshwater stream exiting the cell. (b) During galvanostatic charge/discharge cycling the salt concentrations of brine and freshwater stream can be monitored with microfluidic operando conductivity probes to determine important performance metrics. Figure 1

In this thesis work we explored the capability of electrochemical gating to reliably control the ground state of several chosen materials, with a specific focus on the engineering of the superconducting state. We also experimented with different electrolyte compositions in order to best match the electrochemical requirements of the various materials under study (e.g., chemical stability). In the presentation of the results, we will move from the thicker, bulk-like materials down to the truly two-dimensional properties of thin exfoliated single crystals. Chapter 1 presents a general analysis of the field-effect technique based on an electrolytic gate. We discuss the basic principle that allows for the existence of ultrahigh electric fields at the device surface, together with the several pratical limitations and criticalities the technique entails. In particular, we consider the critical distinction between purely electrostatic gating and the regimes where various types of electrochemical interactions are activated between the sample and the electrolyte. We also discuss in detail a purely electrochemical measurement that can be performed on the complete devices in order to determine the amount of charge accumulated in the electric double layer. Chapter 2 shows a selection of our results on superconducting thin films. We analyze extensively the response of conventional BCS superconductor niobium nitride to EDL gating as a function of film thickness (∼ 40−10 nm), and we interpret our data in the framework of a bulk control of the superconducting transition mediated by proximity effect. We then extend our analysis to more complex materials. We show preliminary results on state-of-the-art thin films (∼ 20 nm) of two-gap superconductor magnesium diboride. Finally, we consider thin films of iron-based superconductor barium iron arsenide and show how its Tc can be modulated by the electric field only in the smallest thicknesses available by state-of-the-art growth techniques (∼ 10 nm). Chapter 3 presents our results on thin flakes (∼ 5−10 nm) of transition metal dichalcogenides. We explore via EDL gating the valley occupation in the conduction and of semiconducting molybdenum and tungsten disulphides at high carrier densities. We show preliminary evidence linking the emergence of EDL-induced superconductivity with the population of secondary minima in the bandstructure for molybdenum disulphide. We also exploit electrochemical gating beyond the electrostatic regime to perform field-assisted intercalation of molybdenum disulphide with alkali ions, in an effort to demonstrate both surface and bulk gate-controlled superconductivity in the same device architecture. We find preliminary evidence for the onset of a possible Charge-Density-Wave phase at very high ion doping. Chapter 4 is entirely devoted to our results on few-layer graphene. While we did not observe any gate-induced superconductivity (down to T= 3.5 K) even at the highest induced carrier densities ∼ 6 · 1014 cm-2, we were able to extensively study the dominant scattering mechanisms both in the high and low temperature regimes; in particular, we showed that inelastic scattering for T . 90 K is dominated by electron-electron collisions, in contrast with what was found in the literature for single-layer graphene. Moreover, we observed the emergence of quantum coherence phenomena (weak localization) for T . 20 K in these previously unreached conditions of ultrahigh carrier doping. Finally, in the Conclusions we summarize the most significant results obtained during this thesis work together with the questions that are still left open. Furthermore, we consider some perspectives and future lines of research that could be pursued in the framework of electrolyte gating.