Sulfonic acid-functionalized graphene (S-graphene) is employed as a promising inorganic filler as well as a solid acid proton conducting medium to realize a composite membrane with Nafion for polymer ...electrolyte fuel cell (PEFC) applications under reduced relative humidity (RH). The functionalization of graphene is performed by sulfonic acid-containing aryl radicals to increase the number of sulfonate groups per unit volume of a domain. A Nafion–S-graphene composite membrane is obtained by embedding S-graphene in Nafion, which provides high absorption of water and fast proton-transport across the electrolyte membrane under low RH values. The proton conductivity of the Nafion–S-graphene (1%) composite membrane at 20% RH is 17 mS cm–1, which is five times higher than that of a pristine recast Nafion membrane. PEFCs incorporating the Nafion–S-graphene composite membrane deliver a peak power density of 300 mW cm–2 at a load current density of 760 mA cm–2 while operating at optimum temperature of 70 °C under 20% RH and ambient pressure. By contrast, operating under identical conditions, a peak power density of 220 mW cm–2 is achieved with the pristine recast Nafion membrane. The Nafion–S-graphene composite membrane could be used to address many critical problems associated with commercial Nafion membranes in fuel cell applications.
Conventional lithium-ion liquid-electrolyte batteries are widely used in portable electronic equipment such as laptop computers, cell phones, and electric vehicles; however, they have several ...drawbacks, including expensive sealing agents and inherent hazards of fire and leakages. All solid state batteries utilize solid state electrolytes to overcome the safety issues of liquid electrolytes. Drawbacks for all-solid state lithium-ion batteries include high resistance at ambient temperatures and design intricacies. This paper is a comprehensive review of all aspects of solid state batteries: their design, the materials used, and a detailed literature review of various important advances made in research. The paper exhaustively studies lithium based solid state batteries, as they are the most prevalent, but also considers non-lithium based systems. Non-lithium based solid state batteries are attaining widespread commercial applications, as are also lithium based polymeric solid state electrolytes. Tabular representations and schematic diagrams are provided to underscore the unique characteristics of solid state batteries and their capacity to occupy a niche in the alternative energy sector.
•A comprehensive review of all aspects of solid state batteries: design, materials.•Tabular representations to underscore the characteristics of solid state batteries.•Solid state electrolytes to overcome the safety issues of liquid electrolytes.
Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement ...and, in certain cases, entanglement sudden death. Kim et al propose and demonstrate a scheme to protect entanglement from de-coherence.
Abstract
Multiphoton interference is an important phenomenon in modern quantum mechanics and experimental quantum optics, and it is fundamental for the development of quantum information science and ...technologies. Over the last three decades, several theoretical and experimental studies have been performed to understand the essential principles underlying such interference and to explore potential applications. Recently, the two-photon interference (TPI) of phase-randomized weak coherent states has played a key role in the realization of long-distance quantum communication based on the use of classical light sources. In this context, we investigated TPI experiments with weak coherent pulses at the single-photon level and quantitatively analyzed the results in terms of the single- and coincidence-counting rates and one- and two-photon interference-fringe shapes. We experimentally examined the Hong–Ou–Mandel-type TPI of phase-randomized weak coherent pulses to compare the TPI effect with that of correlated photons. Further experiments were also performed with two temporally- and spatially separated weak coherent pulses. Although the observed interference results, including the results of visibility and fringe shape, can be suitably explained by classical intensity correlation, the physics underlying the TPI effect needs to be interpreted as the interference between the two-photon states at the single-photon level within the utilized interferometer. The results of this study can provide a more comprehensive understanding of the TPI of coherent light at the single-photon level.
We report a source of polarization-entangled photon pairs in the 1550-nm telecommunication band, which is based on non-collinear spontaneous parametric down-conversion in a periodically poled lithium ...niobate crystal pumped by picosecond pulses. This source is realized utilizing a polarization-based Sagnac interferometer employing a type-0 non-collinear quasi-phase-matching configuration. Polarization entanglement is verified through measurement of the polarization-correlation interference fringes with visibility >96% and by testing the experimental violation of the Clauser-Horne-Shimony-Holt (CHSH) form of Bell's inequality. The CHSH-Bell parameter S is found to be 2.72 ± 0.04, with 18 standard deviations from the statistical uncertainty.
Neural circuits, governed by a complex interplay between excitatory and inhibitory neurons, are the substrate for information processing, and the organization of synaptic connectivity in neural ...network is an important determinant of circuit function. Here, we analyzed the fine structure of connectivity in hippocampal CA1 excitatory and inhibitory neurons innervated by Schaffer collaterals (SCs) using mGRASP in male mice. Our previous study revealed spatially structured synaptic connectivity between CA3 and CA1 pyramidal cells (PCs). Surprisingly, parvalbumin-positive interneurons (PVs) showed a significantly more random pattern spatial structure. Notably, application of Peters' rule for synapse prediction by random overlap between axons and dendrites enhanced structured connectivity in PCs, but, by contrast, made the connectivity pattern in PVs more random. In addition, PCs in a deep sublayer of striatum pyramidale appeared more highly structured than PCs in superficial layers, and little or no sublayer specificity was found in PVs. Our results show that CA1 excitatory PCs and inhibitory PVs innervated by the same SC inputs follow different connectivity rules. The different organizations of fine scale structured connectivity in hippocampal excitatory and inhibitory neurons provide important insights into the development and functions of neural networks.
Understanding how neural circuits generate behavior is one of the central goals of neuroscience. An important component of this endeavor is the mapping of fine-scale connection patterns that underlie, and help us infer, signal processing in the brain. Here, using our recently developed synapse detection technology (mGRASP and neuTube), we provide detailed profiles of synaptic connectivity in excitatory (CA1 pyramidal) and inhibitory (CA1 parvalbumin-positive) neurons innervated by the same presynaptic inputs (CA3 Schaffer collaterals). Our results reveal that these two types of CA1 neurons follow different connectivity patterns. Our new evidence for differently structured connectivity at a fine scale in hippocampal excitatory and inhibitory neurons provides a better understanding of hippocampal networks and will guide theoretical and experimental studies.
In this work, NbOx-based selector devices were fabricated by sputtering deposition systems. Metal-to-insulator transition characteristics of the device samples were investigated depending on the ...oxygen flow rate (3.5, 4.5, and 5.5 sccm) and the deposition time. The device stack was scanned by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The yields, including MIT, nonlinear, and Ohmic, in working devices with different deposition conditions were also evaluated. Moreover, we observed the trend in yield values as a function of selectivity. In addition, the current–voltage (I–V) curves were characterized in terms of DC and pulse endurance. Finally, the switching speed and operating energies were obtained by applying a triangular pulse on the devices, and the recovery time and drift-free characteristics were obtained by the paired pulses.
Proton exchange membranes are an essential component of proton-exchange membrane fuel cells (PEMFC). Their performance is directly related to the development of ionic channel networks through ...hydration. Current sensing atomic force microscopy (CSAFM) can map the local conductance and morphology of a sample surface with sub-nano resolution simultaneously by applying a bias voltage between the conducting tip and sample holder. In this study, the ionic channel network variation of Nafion by hydration has been quantitatively characterized based on the basic principles of electrodynamics and CSAFM. A nano-sized PEMFC has been created using a Pt-coated tip of CSAFM and one side Pt-coated Nafion, and studied under different relative humidity (RH) conditions. The results have been systematically analyzed. First, the morphology of PEMFC under each RH has been studied using line profile and surface roughness. Second, the CSAFM image has been analyzed statistically through the peak value and full-width half-maximum of the histograms. Third, the number of protons moving through the ionic channel network (NPMI) has been derived and used to understand ionic channel network variation by hydration. This study develops a quantitative method to comprehend variations in the ionic channel network by calculating the movement of protons into the ionic channel network based on CSAFM images. To verify the method, a comparison is made between the NPMI and the changes in proton conductivity under different RH conditions and it reveals a good agreement. This developed method can offer a quantitative approach for characterizing the morphological structure of PEM. Also, it can provide a quantitative tool for interpretating CSAFM images.
Understanding the ionic structure and charge transport on proton exchange membranes (PEMs) is crucial for their characterization and development. Electrostatic force microscopy (EFM) is one of the ...best tools for studying the ionic structure and charge transport on PEMs. In using EFM to study PEMs, an analytical approximation model is required for the interoperation of the EFM signal. In this study, we quantitatively analyzed recast Nafion and silica-Nafion composite membranes using the derived mathematical approximation model. The study was conducted in several steps. In the first step, the mathematical approximation model was derived using the principles of electromagnetism and EFM and the chemical structure of PEM. In the second step, the phase map and charge distribution map on the PEM were simultaneously derived using atomic force microscopy. In the final step, the charge distribution maps of the membranes were characterized using the model. There are several remarkable results in this study. First, the model was accurately derived as two independent terms. Each term shows the electrostatic force due to the induced charge of the dielectric surface and the free charge on the surface. Second, the local dielectric property and surface charge are numerically calculated on the membranes, and the calculation results are approximately valid compared with those in other studies.
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