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Cubic Li7La3Zr2O12 (LLZO) garnets are exceptionally well suited to be used as solid electrolytes or protecting layers in "Beyond Li-ion Battery" concepts. Unfortunately, cubic LLZO is not stable at room temperature (RT) and has to be stabilized by supervalent dopants. In this study we demonstrate a new possibility to stabilize the cubic phase at RT via substitution of Zr(4+) by Mo(6+). A Mo(6+) content of 0.25 per formula unit (pfu) stabilizes the cubic LLZO phase, and the solubility limit is about 0.3 Mo(6+) pfu. Based on the results of neutron powder diffraction and Raman spectroscopy, Mo(6+) is located at the octahedrally coordinated 16a site of the cubic garnet structure (space group Ia-3d). Since Mo(6+) has a smaller ionic radius compared to Zr(4+) the lattice parameter a0 decreases almost linearly as a function of the Mo(6+) content. The highest bulk Li-ion conductivity is found for the 0.25 pfu composition, with a typical RT value of 3.4 × 10(-4) S cm(-1). An additional significant resistive contribution originating from the sample interior (most probably from grain boundaries) could be identified in impedance spectra. The latter strongly depends on the prehistory and increases significantly after annealing at 700 °C in ambient air. Cyclic voltammetry experiments on cells containing Mo(6+) substituted LLZO indicate that the material is stable up to 6 V.

We report on a quick, simple, and cost-effective solution-phase approach to prepare centimeter-sized morphology-graded vertically aligned Si nanowire arrays. Gradients in the nanowire diameter and shape are encoded through the macroscale substrate via a "dip-etching" approach, where the substrate is removed from a KOH etching solution at a constant rate, while morphological control at the nanowire level is achieved via sequential metalassisted chemical etching and KOH etching steps. This combined approach provides control over light absorption and reflection within the nanowire arrays at both the macroscale and nanoscale, as shown by UV−vis spectroscopy and numerical three-dimensional finite-difference time-domain simulations. Macroscale morphology gradients yield arrays with gradually changing optical properties. Nanoscale morphology control is demonstrated by synthesizing arrays of bisegmented nanowires, where the nanowires are composed of two distinct segments with independently controlled lengths and diameters. Such nanowires are important to tailor light−matter interactions in functional devices, especially by maximizing light absorption at specific wavelengths and locations within the nanowires.

The solvation structure around the Li + ion in a mixed cyclic/linear carbonate solution, an important factor for the performance of lithium-based rechargeable batteries, is examined by measuring and analyzing the noncoincidence effect observed for the CO stretching Raman band. This technique has the advantage of perceiving relative distances and orientations of solvent molecules clustering around an ion in the first solvation shell and, hence, of developing information on the solvation structure along the wavenumber axis rather than along the intensity axis of the spectra. It is shown that, taking the solution of Li + ClO 4 − in the 1:1 mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) as an example case, the Li + ion is preferentially solvated by PC molecules [primarily as (PC) 3 (DEC) 1 Li + ] and is totally protected from direct interaction (contact ion pairing) with the ClO 4 − ion. The solvation structures in neat PC and neat DEC solvents are also discussed.I on solvation is a central, and still an open, issue in many chemical, biochemical, and electrochemical processes. One of those important processes would be the functioning of lithium-based rechargeable batteries. 1−3 Their performance depends on the electrode materials and processes on the one hand and on the charge carrier concentration and mobility in the electrolyte solution on the other hand. With regard to the latter, high charge density of the Li + ion should be sufficiently stabilized, and at the same time, the electrolyte solution should have sufficiently high fluidity. A usual practice to make these two factors compatible is to employ a mixed solvent, consisting of a highly dipolar liquid such as a cyclic carbonate stabilizing the high charge density (but highly viscous) and a liquid of lower viscosity such as a linear carbonate (being less dipolar). Quite often ethylene or propylene carbonate (with dielectric constant ε = 65−90 and viscosity η ≅ 2.5 cP, abbreviated as EC and PC) is used for the former, and dimethyl, diethyl, or ethyl methyl carbonate (with ε ≅ 3 and η = 0.6−0.9 cP, abbreviated as DMC, DEC, and EMC) is used for the latter.The solvation structure around the Li + ion, especially that of the first solvation shell, has been suggested to be important for the interphase chemistry on the electrodes. 4−6 The use of a mixed solvent introduces a complexity in this. One controversial subject in this regard is the presence/absence of the preferential solvation and (if present) its nature for the Li + ion in a mixed cyclic/linear carbonate solution. 7−19 On the basis of electrospray ionization mass spectroscopy (ESI-MS), 7,8 it has been suggested that there is a strong preferential solvation for Li + in EC/EMC, with the Li + (EC) 2 species as the main ingredient. 7 The same type of preferential solvation (i.e., with a higher population of cyclic carbonate around the ion than in the bulk) has also been suggested in some NMR studies 9−11 but with a much larger total solvation number (≥6). 9,20 It has been argued that some...

The concentration dependence of the Raman noncoincidence effect (NCE) of the C-O and O-H stretching bands of methanol is investigated in methanol/CCl 4 mixtures in the range of 1.0 g x m g 0.1, where x m is the mole fraction of methanol, by performing Raman spectroscopic measurements and molecular dynamics (MD) simulations. Band asymmetry observed for both bands is carefully taken into account. The experimental and simulation results are in satisfactory agreement with each other. For the C-O stretching band, it is observed that the magnitude of the negative NCE gets larger upon dilution in CCl 4 down to x m ∼ 0.2, contrary to the expectation of becoming smaller from simple guess that the NCE arises from intermolecular vibrational resonant interactions between methanol molecules, which, on average, get separated from each other upon dilution. For the O-H stretching band, the magnitude of the positive NCE remains almost the same upon dilution down to x m ∼ 0.3. These apparently peculiar experimental results are reasonably explained by the MD simulations on the basis of the transition dipole coupling (TDC) mechanism of intermolecular resonant vibrational interactions and the simulated hydrogen-bonded liquid structures. In the case of the C-O stretching band, the negative NCE arises mainly from positive vibrational coupling between hydrogen-bonded pairs of molecules, which is partially canceled by negative vibrational coupling between molecules in different hydrogenbonded chains. In the case of the O-H stretching band, the positive NCE arises predominantly from negative vibrational coupling within hydrogen-bonded chains. As a result, a locally anisotropic change in the liquid structure that occurs upon dilution, in which, around each molecule, intermolecular distances do not change very much along hydrogen-bond directions but do change significantly in other directions, gives rise to the apparently peculiar behavior of the NCE described above.

Raman spectra of a range of differently aged samples of natural resins (recent resins, copals, fossils resins from Tertiary to Early Cretaceous age) were taken for a comparative study of the age‐induced maturation processes of the resins. It can be shown that a decrease in band intensity at around 1640 cm−1 due to loss of ν(CC) stretching vibrations, together with other spectral details, is correlated with the increase in age of the resins. Copyright © 2001 John Wiley & Sons, Ltd.

The nu(C=O) Raman band frequencies of acetone have been analyzed to separate the contributions of the environmental effect and the vibrational coupling to the gas-to-liquid frequency shifts of this band and to elucidate the changes in these two contributions upon dilution in DMSO. We have measured the frequencies of the nu((12)C=O) band in acetone/DMSO binary mixtures, the nu((13)C=O) band of the acetone-(13)C=O present as a natural abundance isotopic impurity in these mixtures, and both the nu((12)C=O) and nu((13)C=O) bands in the acetone-(12)C=O/acetone-(13)C=O isotopic mixtures at infinite dilution. These frequencies are compared with those of the nu((12)C=O) band in the acetone/CCl(4) binary mixtures measured previously. We have found the following three points: (i) The negative environmental contribution for the nu((12)C=O) oscillator of acetone completely surrounded by DMSO is reduced in magnitude by +5.5 cm(-1) and +7.8 cm(-1) upon the complete substitution of DMSO with acetone and CCl(4) molecules, respectively, indicating the progressive reduction of the attractive forces exerted by the environment on the nu((12)C=O) mode of acetone. (ii) In DMSO and other solvents, the contribution of the vibrational coupling to the frequency of the isotropic Raman nu((12)C=O) band of acetone becomes progressively more negative with increasing acetone concentration up to a value of -5.5 cm(-1), while the contribution to the frequency of the anisotropic Raman band remains approximately unchanged. The only difference resides in the curvatures of the concentration dependencies of these contributions which depend on the relative solute/solvent polarity. (iii) The noncoincidence effect (separation between the anisotropic and isotropic Raman band frequencies) of the nu(C=O) mode in the acetone/DMSO mixtures exhibits a downward (concave) curvature, in contrast to that in the acetone/CCl(4) mixtures, which shows an upward (convex) curvature. This result is supported by MD simulations and by theoretical predictions and is interpreted as arising from the reduction and enhancement of the short-range orientational order of acetone in the acetone/DMSO and acetone/CCl(4) mixtures, respectively.

Evidence for the widespread occurrence of extraterrestrial halite, particularly on Mars, has led to speculations on the possibility of halophilic microbial forms of life; these ideas have been strengthened by reports of viable haloarchaea from sediments of geological age (millions of years). Raman spectroscopy, being a sensitive detection method for future astrobiological investigations onsite, has been used in the current study for the detection of nine different extremely halophilic archaeal strains which had been embedded in laboratory-made halite crystals in order to simulate evaporitic conditions. The cells accumulated preferentially in tiny fluid inclusions, in simulation of the precipitation of salt in natural brines. FT-Raman spectroscopy using laser excitation at 1064 nm and dispersive micro Raman spectroscopy at 514.5 nm were applied. The spectra showed prominent peaks at 1507, 1152 and 1002 cm −1 which are attributed to haloarchaeal C 50 carotenoid compounds (mainly bacterioruberins). Their intensity varied from strain to strain at 1064-nm laser excitation. Other distinguishable features were peaks due to peptide bonds (amide I, amide III) and to nucleic acids. No evidence for fatty acids was detected, consistent with their general absence in all archaea.These results contribute to a growing database on Raman spectra of terrestrial microorganisms from hypersaline environments and highlight the influence of the different macromolecular composition of diverse strains on these spectra.