Ion Conduction in Composite Polymer Electrolytes: Potential Electrolytes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are expected to become alternatives to lithium-ion batteries (LIBs) as next-generation rechargeable batteries, owing to abundant sodium sources and low cost. However, SIBs still use liquid organic electrolytes (LOEs), which are highly flammable and have the tendency to leak. Although inorganic solid electrolytes (ISEs) and solid polymer electrolytes (SPEs) have been investigated for many years, given their higher safety level, neither of them is likely to be commercialized because of the rigidity of ISEs and the low room-temperature ionic conductivity of SPEs. During the last decade, composite polymer electrolytes (CPEs), composed of ISEs and SPEs, exhibiting both relatively high ionic conductivity and flexibility, have gained much attention and are considered as promising electrolytes. However, the ionic conductivities of CPEs are still unsatisfactory for practical application. Hence, this Review focuses on the principle of sodium ion conductors and particularly on recent investigations and development of CPEs.

A facile fabrication procedure for platinum nanoprobes with high-aspect-ratio and low tip radii via electrochemical etching.

Herein, we propose a facile fabrication procedure for platinum (Pt) nanoprobes. Our approach consists in performing a one-step electrochemical etching using a mixture of DI water, acetone, and CaCl2. Our technique is self-terminated and thus does not necessitate a cut-off circuit nor other sophisticated equipment or set-up commonly used in the fabrication process of Pt nanoprobes. The Pt nanoprobes thereby manufactured demonstrate small tip radii, a high aspect-ratio, no detectable surface contamination, and good reproducibility.

The effects of thin film homogeneity on the performance of ferroelectric tunnel junctions.

The compelling physical properties of the recently discovered ferroelectric phase in thin film Hf x Zr1-x O2 have opened a window for applications such as non-volatile resistive switching memory devices with high retention known as ferroelectric tunnel junctions. In this article, we investigate the stability of these two-terminal, polarization induced resistance-switching devices with respect to the statistical reproducibility of constitutive electrical parameters based on surface thickness inhomogeneities. We provide a straightforward, quantitative model to estimate tunneling currents dependent on thickness variations, and the resulting tunneling electroresistance (TER) ratios and breakdown probability. An analytical expression for the probability distribution of tunneling currents for normally distributed thicknesses is given. Using material parameters of a TiN/HZO/Pt heterostructure, practical design requirements are deduced and an estimation with respect to the surface roughness is given for practical ferroelectric layer thicknesses and voltages below 4 nm and 1 V, respectively. In this regime, the simple model of a ballistic, direct tunneling mechanism can be used to adequately model the thickness and voltage dependence of the resistivity.

Optical and electrical properties of MoO2 and MoO3 thin films prepared from the chemically driven isothermal close space vapor transport technique.

Chemically-driven isothermal close space vapour transport was used to prepare pure MoO2 thin films which were eventually converted to MoO3 by annealing in air. According to temperature-dependent Raman measurements, the MoO2/MoO3 phase transformation was found to occur in the 225 °C-350 °C range while no other phases were detected during the transition. A clear change in composition as well as noticeable modifications of the band gap and the absorption coefficient confirmed the conversion from MoO2 to MoO3. An extensive characterization of these two pure phases was carried out. In particular, a procedure was developed to determine the dispersion relation of the refractive index of MoO2 from the shift of the interference fringes of the used SiO2/Si substrate. The obtained data of the refractive index was corrected taking into account the porosity of the samples calculated from elastic backscattering spectrometry. The Debye temperature and the residual resistivity were extracted from the electrical resistivity temperature dependence using the Bloch-Grüneisen equation. MoO3 converted samples presented a very high resistivity and a typical semiconducting behavior. They also showed intense and broad luminescence spectra composed by several contributions whose temperature behavior was examined. Furthermore, surface photovoltage spectra were taken and their relation with the photoluminescence is discussed.

B-site modified photoferroic Cr3+-doped barium titanate nanoparticles: microwave-assisted hydrothermal synthesis, photocatalytic and electrochemical properties.

We report on the synthesis of photoferroic Cr3+-doped BaTiO3 nanoparticles with nominal Cr content ranging from 2-8 mol% by a microwave-assisted hydrothermal method. The absorption properties of the doped systems are significantly enhanced due to the d-d band transition of Cr3+/4+. The structural properties of the materials are examined on the basis of lattice distortions given by the tolerance factor and microstrain. Raman scattering provides complementary information on the lattice vibrations indicating a softening of the longitudinal optic (LO) phonon mode located at 716 cm-1 with increasing Cr concentration. The charge transport properties investigated through electrochemical impedance spectroscopy (EIS) demonstrate that there is a reduction in the charge transfer resistance from 5.2 Ω to 4.3 Ω for the undoped and 4 mol% Cr3+-doped respectively, which favors the degradation kinetics. The photo-oxidation ability of the systems is evaluated by time evolution of photodegradation of methyl orange under standardized solar irradiation. The experimental results confirm that the best photocatalytic performance is achieved with the 4 mol% Cr3+-doped BaTiO3 nanoparticles, which is ∼2.7 times higher than for the undoped sample. Evidence of superoxide radical being the dominant active species is provided by in situ reactive oxide species (ROS) capture experiments.

Note: Controlling the length of plasmonic tips obtained by pulsed electrochemical etching.

We present a method to control the length of plasmonic gold tips through pulsed electrochemical etching. This method uses a cut-off circuit to interrupt the etching when the desired length is achieved, paving the way to tune the plasmonic properties of these tips through their shape. The control of the tip length by monitoring the cell voltage is the result of a study of the etching dynamics. The resulting tips possess a low apex radius and a small opening angle, allowing for high spatial resolution both in topography and in near-field imaging. The plasmonic behavior was confirmed in tip-enhanced Raman spectroscopy.

Near-field chemical mapping of gold nanostructures using a functionalized scanning probe.

We report on photochemical and photophysical properties produced by Surface Plasmon Resonance (SPR) on metallic nanograins by means of high resolution Functionalized Tip-Enhanced Raman Spectroscopy (F-TERS). This technique relies on a sharp gold tip functionalized with Raman-active molecules to be scanned relatively to plasmonic hot-spots on a surface. We describe the local variation of plasmon-induced Raman enhancement on the surface of nanostructures that also affects the photochemistry while the quantitative interpretation of peak intensities requires the consideration of surface topography near the tip apex. Our F-TERS maps show Raman modes of hot electron reduction of 4-nitrothiophenol (4-NTP) molecules on the tip and indicate at least partial photochemical dimerization. An apparent photo-induced reversibility of this dimerization can be conservatively explained by a local topography feature that we simulate in a finite element environment. Our experimental results reveal a spatial resolution of approximately 10 nm, corresponding to a few hundred 4-NTP molecules exposed to the near-field.

Composition variation in Al-based dilute nitride alloys using apertureless scanning near-field optical microscopy.

We use apertureless scanning near-field optical microscopy to study the phase separation in chemical beam epitaxy grown Al0.1Ga0.9NxAs1-x alloys. Pits attributed to nitrogen-clustering observed on the Al0.1Ga0.9NxAs1-x surface grown at 420 °C become larger at higher growth temperatures, and 3D islands appear on the surface at 565 °C. Atomic force microscopy phase measurements reveal a composition difference between the islands and the pits, whereas the sample grown at 420 °C appears to be homogeneous. Confocal Raman spectra show that all the N atoms are bonded to Al instead of Ga. Using apertureless scanning near-field optical microscopy, the luminescence of a gold tip is mapped over the surface of the sample grown at 565 °C. We extract the shift of the tip's surface plasmon resonance and determine the variation in the refractive index between the islands and the pits to be close to 0.2. Numerical simulations of the tip luminescence while in contact with the sample predict a similar variation of ∼0.3 in the refractive indices between AlGaAs islands and AlN pits, a substantially smaller value than the difference in the bulk refractive indices of the two media (∼1.8), which we attribute to a convolution of material distribution in an uneven topography. The excellent agreement between simulation and experiments supports the hypothesis of nitrogen-clustering in the pits.

High resolution scanning near field mapping of enhancement on SERS substrates: comparison with photoemission electron microscopy.

The need for a dedicated spectroscopic technique with nanoscale resolution to characterize SERS substrates pushed us to develop a proof of concept of a functionalized tip-surface enhanced Raman scattering (FTERS) technique. We have been able to map hot spots on semi-continuous gold films; in order to validate our approach we compare our results with photoemission electron microscopy (PEEM) data, the complementary electron microscopy tool to map hot spots on random metallic surfaces. Enhanced Raman intensity maps at high spatial resolution reveal the localisation of hotspots at gaps for many neighboring nanostructures. Finally, we compare our findings with theoretical simulations of the enhancement factor distribution, which confirms a dimer effect as the dominant origin of hot spots.

A near field optical image of a gold surface: a luminescence study.

This paper addresses recent experimental findings about luminescence of a gold tip in near-field interaction with a gold surface. Our electrochemically etched gold tips show a typical, intrinsic luminescence that we exploit to track the plasmon resonance modeled by a Lorentzian oscillator. Our experimental device is based on a spectrometer optically coupled to an atomic force microscope used in tuning fork mode. Our measurements provide evidence of a strong optical coupling between the tip and the surface. We demonstrate that this coupling strongly affects the luminescence (intensity, wavelength and FHWM) as a function of the tip position in 2D maps. The fluctuation of these parameters is directly related to the plasmonic properties of the gold surface and is used to qualify the optical near field enhancement (which subsequently plays the predominant role in surface enhanced spectroscopies) with a very high spatial resolution (typically around 20 nm). We compare these findings to the independently recorded near-field scattered elastic Rayleigh signal.

Coexistence of antiferromagnetic and ferromagnetic orders at remanent state in epitaxial multiferroic Bi2FeCrO6 nanostructures.

We report the local electronic and magnetic properties of Bi(2)FeCrO(6) nanostructures by element-specific polarized x-ray techniques. Sizable magnetic ordering in the remanent state is observed at room temperature for both Fe and Cr ions. The Bi(2)FeCrO(6) system offers an example of d(5)-d(3) magnetic superexchange interaction with a magnetic order for both Fe and Cr, which are both formally in the  + 3 valence state. The results suggest a coexistence of antiferromagnetic and ferromagnetic superexchange interaction between Fe and Cr spins in the nanostructures at the remanent state and at room temperature.

Population estimates for biomarkers of exposure to cigarette smoke in adult U.S. cigarette smokers.

INTRODUCTION: There are about 4,800 different chemical constituents in cigarette smoke. Therefore, the total systemic exposure evaluation of the population of smokers to cigarette smoke is challenging. Measurement of biomarkers as surrogates of cigarette smoke constituents is a realistic approach to assess exposure. OBJECTIVE: To estimate cigarette smoke exposure of the U.S. smoker population. METHODS: Stratified, cross-sectional, multicenter design (39 sites in 31 states); 3,585 adult cigarette smokers and 1,077 nonsmokers. Biomarkers were determined from 24-hr urine collections or blood samples. Population estimates were generated by weighting sample data with weights from a large U.S. probability sample (Behavioral Risk Factor Surveillance System). RESULTS: The adult smoker population estimates for tobacco-specific biomarkers were nicotine equivalents 13.3 mg/24 hr (SE 0.14), serum cotinine 184 ng/ml (1.8), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol 439 ng/24 hr (5.5). The population estimates for smokers and nonsmokers for nontobacco-specific biomarkers were 1-hydroxypyrene 317 (6.8) and 110 (7.1) ng/24 hr, 4-aminobiphenyl Hb adducts 43.1 (1.04) and 11.4 (1.5) pg/g Hb, carboxyhemoglobin 5.26(0.04) in percent of hemoglobin saturation and 1.45(0.02), 3-hydroxypropylmercapturic acid 2,030 (24) and 458 (17) microg/24 hr, monohydroxy-butenyl-mercapturic acid 3.61 (0.1) and 0.30 (0.02) microg/24 hr, and dihydroxy-butyl-mercapturic acid 556 (4.9) and 391 (5.5) microg/24 hr. On average, young adult smokers had lower exposure than older smokers; female smokers had lower exposure than males, and Black smokers had lower exposure than Whites. DISCUSSION: This study estimated the population exposure to cigarette smoke constituents in adult U.S. smokers and identified significant differences between subpopulations. The data may serve as a reference for monitoring the impact of changes in cigarette consumption and the introduction of potentially reduced exposure cigarettes.

The relationship between smoking machine derived tar yields and biomarkers of exposure in adult cigarette smokers in the US.

UNLABELLED: Comprehensive data on human exposure to smoke constituents from different machine-measured tar yield cigarettes is limited. METHODS: This study used a stratified, cross-sectional, multi-center design to estimate biomarkers of exposure (BOE) from nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), pyrene, CO, acrolein, and 1,3-butadiene and their relationship to tar yield categories of cigarette in adult smokers in the U.S. 3625 adults smokers were enrolled into four tar categories < or =2.9 mg (T1), 3.0-6.9 mg (T2), 7.0-12.9 mg (T3), and > or =13.0mg (T4). Biomarkers were measured in blood (carboxyhemoglobin, 4-aminobiphenyl-hemoglobin (4-ABP-Hb)-adducts, serum cotinine) and 24h urine (nicotine and five metabolites, calculated as nicotine equivalents (NE), NNAL, 1-OH-pyrene, 3-HPMA, MHBMA and DHBMA). Data were analyzed using analysis of covariance (ANCOVA). RESULTS: Tar was a significant factor for most biomarkers in the ANCOVA models. The largest least square mean differences between tar categories was 35% for NE per day, 28% for NE per cigarette, 36% for serum cotinine, 42% for NNAL per day, 29% for NNAL per cigarette, 26% for 1-OHP, 24% for COHb, 14% for 3-HPMA and 40% for 4-ABP-Hb. Variability in BOE ranged from 41% to 154% CV. CONCLUSIONS: There was a statistically significant effect of machine-measured tar yield on most BOE, which were generally lower with lower tar yield.

Short-term exposure evaluation of adult smokers switching from conventional to first-generation electrically heated cigarettes during controlled smoking.

This randomized, controlled study in 110 male and female adult smokers evaluated biomarkers of tobacco smoke exposure (carbon monoxide [CO], carboxyhemoglobin [CO-Hb], nicotine, urine mutagenicity) under controlled smoking conditions when adult smokers of 1 conventional cigarette brand (CC1) were switched to an electrically heated cigarette smoking system (EHCSS) or a low-tar conventional cigarette (CC2). Baseline exposure was determined while all subjects smoked CC1. Subjects then were stratified for gender and cigarette consumption and randomized to 1 of 5 groups-EHCSS1, EHCSS2, CC1, CC2, or no smoking-and monitored for 8 days. Compared to baseline, biomarkers of exposure on day 8 decreased 53% to 93% (P < .0001) for EHCSS groups and 18% to 39% (P < .02) for CC2. Environmental tobacco smoke arising from the smoking activities of the different study groups was measured in the air of a separate smoking room over 1-hour periods. Concentrations of respirable suspended particulates in both EHCSS groups were about 90% lower than in the CC1 and CC2 groups, similar to the 95% reduction in the no-smoking group. CO was undetectable in the EHCSS and no-smoking groups. Results from this short-term clinical study indicate that switching from a conventional cigarette to a first-generation EHCSS reduces the generation of environmental tobacco smoke and can reduce the exposure to the measured, potentially harmful constituents in tobacco smoke if smokers do not compensate by numbers of cigarettes. The study design was found to be suitable for the evaluation of the exposure of adult smokers to the measured smoke constituents and to allow the differentiation of different cigarette designs.