Electron microscopy has enabled atomic resolution imaging of matter. However, unlike optical spectroscopic imaging, traditional electron microscopes provide limited spectroscopic information in terms of their energy resolution. Only recently, owing to advances in monochromated STEM-EELS, have transmission electron microscopes (TEMs) been able to attain a high energy resolution. We recently proposed combining spectrally selective photoexcitation with HRTEM to achieve sub-nanometer scale optical imaging, a technique we called photoabsorption microscopy using electron analysis (PAMELA). To realize PAMELA-TEM experimentally, we constructed a TEM holder with an optical feedthrough, capable of photoexciting materials with different wavelengths. In this article, we describe our process for designing and fabricating an optical TEM specimen holder, highlighting important aspects of the design.

The production of Amarone wine is governed by a disciplinary guideline to preserve its typical features; however, postharvest infections by the fungus Botrytis cinerea (B. cinerea) not only represent a phytosanitary problem but also cause a significant loss of product. In this study, we tested a treatment with mild ozoniztion on grapes for Amarone wine production during withering in the fruttaio (the environment imposed by the disciplinary guideline) and evaluated the impact on berry features by a multimodal imaging approach. The results indicate that short and repeated treatments with low O3 concentrations speed up the naturally occurring berry withering, probably inducing a reorganization of the epicuticular wax layer, and inhibit the development of B. cinerea, blocking the fungus in an intermediate vegetative stage. This pilot study will pave the way to long-term research on Amarone wine obtained from O3-treated grapes.

Polarized optical absorption spectra of single crystals of the two dimorphic Mn2AsO4(OH)-minerals eveite and sarkinite show that minor concentrations of Mn3+ at the octahedral site determine the colour and cause the distinct pleochroism in green and yellow of eveite. In the sarkinite spectra only absorption bands due to spin-forbidden d-d transitions in Mn2+ at six- and five-coordinated sites are observed, which produce a weak flesh-red mineral colour and a very faint pleochroism.

The Usambara effect, i.e. a change of tourmaline colour from deep-green to dark-red with increasing path length of light, has been studied by optical absorption spectroscopy and colourimetric calculations on a sample of Tanzanian tourmaline of predominant dravite composition with 0.12 apfu Cr. For comparison a dark-green vanadium-bearing tourmaline from Tanzania (0.05 apfu V), which does not show such an effect, was also investigated. As established, the Usambara effect, by its nature, is closely related to the alexandrite effect, although in this case the colour change is not caused by change of spectral composition of the light of illumination, but by spectral positions of the spin-allowed absorption bands of Cr3+, a specific ratio of light transmission in two windows of transparency, green and red, and by non-linear, exponential dependence of the light transmittance on the thickness of sample. A threshold chromium content must be exceeded for the Usambara effect to show, that is, sufficient chromium for there to be two deep and well-demarcated windows of transparency in the visible range. The overall colouration results from mixing of two additive colours coming through the windows of transparency. A dark-green chromium-bearing tourmaline from the Ural Mountains (0.40 and 0.20 apfu Cr and Fe, respectively) shows how admixtures of other chromophore ions, namely, Fe2+ and Fe3+, can suppress the Usambara effect in tourmaline.

We propose that nanophase iron-oxide-bearing materials provided important niches for ancient photosynthetic microbes on the Earth that ultimately led to the oxygenation of the Earth's atmosphere and the formation of iron-oxide deposits. Atmospheric oxygen and ozone attenuate ultraviolet radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose early and played a critical role in subsequent evolution. Of primary importance was protection below 290 nm, where peak nucleic acid (~260 nm) and protein (~280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal ultraviolet radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Furthermore, they were available in early environments, and are synthesized by many organisms. Based on experiments using nanophase ferric oxide/oxyhydroxide minerals as a sunscreen for photosynthetic microbes, we suggest that iron, an abundant element widely used in biological mechanisms, may have provided the protection that early organisms needed in order to be able to use photosynthetically active radiation while being protected from ultraviolet-induced damage. The results of this study are broadly applicable to astrobiology because of the abundance of iron in other potentially habitable bodies and the evolutionary pressure to utilize solar radiation when available as an energy source. This model could apply to a potential life form on Mars or other bodies where liquid water and ultraviolet radiation could have been present at significant levels. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the photosynthetic organisms, Euglena sp. and Chlamydomonas reinhardtii, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides.

The GexGa5Se(95−x) glasses, where x = 20, 22.5, 25, 27.5, 29.17, 30, 32.5, and 35, all doped with 0.05 mol% Dy3+ were prepared and studied. Thermal stabilities, optical properties, and 1.3 μm emission properties of the glasses were investigated. Strong fluorescence centered at 1.34 μm with a bandwidth of 92 nm was observed. Three phenomenological intensity parameters were obtained: Ω2 =12.64 × 10−20, Ω4 =2.94 × 10−20, and Ω6 =1.48 × 10−20 cm2 by Judd–Ofelt analysis. A new method estimating lifetime of overlapping energy level was introduced. Lifetimes of 520 μs were measured for the 1.3 μm transition, and the quantum efficiency was 36.8% according to the new method.

Nano-sized (Y,Gd)2O3:Eu powders were synthesized by a novel co-precipitation processing in which a mixture of ammonium hydroxide and ammonium hydrogen carbonate was adopted as a complex precipitant. Evolution behaviors of precursors during calcinations were studied by means of thermogravimetry-differential scanning calorimetry-mass spectrum, Fourier transform infrared, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy in detail. Nano-sized (Y,Gd)2O3:Eu powder as prepared possessed a primary grain size of about 30 nm and specific surface area of 38 m2/g after being calcined at 850 °C for 2 h, showing much finer grains and less agglomeration. The as prepared nanopowder shows intense luminescence at 611nm under x-ray or ultraviolet excitation. Transparent (Y,Gd)2O3:Eu ceramics can also be fabricated using this high sinterable nanopowder.

The luminescence properties of nanocrystalline Y2O3:Er3+ prepared via wet chemical synthesis were investigated. A broadening of both the reflectance spectrum and 77 K luminescence spectrum (λexc = 488 nm) was observed in the nanocrystalline material compared to bulk Y2O3:Er3+. The spectral broadening was attributed to the presence of Er3+ ions on the surface of the particle, which experienced different crystal fields than the ions buried in the core of the particle. Upconversion was observed in both the bulk and nanocrystal material following excitation with 650-nm or 800-nm radiation. Following excitation with 800-nm radiation, an enhancement of the red (4F9/2 → 4I15/2) upconverted emission was observed and occurred as a result of the (4I9/2, 4I11/2) → (4I13/2, 4F9/2) ion-pair process that directly populated the 4F9/2 state. The magnitude of the red enhancement in the nanocrystalline material prepared via wet chemical synthesis was less than that of the identically doped bulk sample and less still than Y2O3:Er3+ nanocrystals prepared via a combustion synthesis technique. An explanation is proposed to account for the drastic difference in the red upconverted luminescence intensity.

A new approach to general sensors for odors and volatile organic compounds (VOCs) using thin films of chemically responsive dyes as a colorimetric sensor array is described. This optoelectronic “nose,” by using an array of multiple dyes whose colors change based on the full range of intermolecular interactions, provides enormous discriminatory power among odorants in a simple device that can be easily digitally imaged. High sensitivities (ppb) have been demonstrated for the detection of biologically important analytes such as amines, carboxylic acids, and thiols. By the proper choice of dyes and substrate, the array can be made essentially nonresponsive to changes in humidity.

The synthesis and characteristics of strontium borate phosphate phosphors doped with cerium ions were investigated in this study. The synthesis of Sr0.95Ce0.05BPO5 in oxidizing atmosphere results in partial conversion of Ce4+ ions into Ce3+ ions. The luminescent characteristics reveal that Ce3+ ions occupy two principal sites in the host. The dominant emission at 317 nm on 275-nm excitation is attributed to Ce3+ ions located at Sr2+ sites without local charge compensation. The weak emission at 330 nm due to 295-nm excitation is ascribed to Ce3+ ions located at Sr2+ sites in association with charge compensatory vacancy. The reduction of Ce4+ ions to Ce3+ ions occurs in Sr0.95Ce0.05BPO5 heated in the reducing atmosphere. For Sr0.9Ce0.05Na0.05BPO5 and Sr0.9Ce0.05Li0.05BPO5 phosphors, enhancement in luminescence is observed due to the codoping of monovalent ions. The increased luminescence of these phosphors is attributed to the decrease in non-radiative energy transfer.

In this article, we present a study of a new glass system: lead–germanium–tellurite glasses in the form of 0.05K2O–0.1ZnO–0.1BaO–0.2PbO–xGeO2–(0.55 - x)TeO2 with x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.55. Differential temperature analysis of this glass system shows that increasing GeO2 content raises the glass transition temperature (Tg) and suppresses the crystallization tendency in a large temperature range from Tg to the glass melting temperature. The maximum vibrational frequency is intermediate between germanate and fluoride glasses, in the range of 750 cm−1 to 820 cm−1. Subsequently, Optical absorption, photoluminescence, and upconversion fluorescence were measured for Yb3+, Er3+ co-doped lead–tellurium–germanate glasses. It was found that the full width at half-maximum of the fluorescence spectrum at 1534 nm decreases and the measured radiative lifetime increases with the replacement of TeO2 by GeO2. Excitation at 976 nm into the glass system leads to an intense green emission and a relatively weak red emission. With the addition of GeO2, the increase of red fluorescence and the decrease of green emission in intensity are due to the increase of nonradiative transition rates between the 4S3/2 and 4F9/2 states of Er3+ ions. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption process occurs in this glass system excited at 976 nm.

The effect of the doping by compounds with bivalent and trivalent cations (BN, Al2O3, MgO + SiO2) on the diffuse reflectance spectra (ρλ) and the integral solar absorptance (as) and their changes at irradiation (with 30 keV electrons, 3 keV protons, and electromagnetic radiation that imitates solar spectra) of the reflecting thermal control coatings based on ZrO2 powders is examined. The coating based on untreated ZrO2 pigment and the coatings based on the pigments treated with 1 and 3 mass% of Al2O3 nanopowder were subjected to simultaneous action of electrons, protons, and electromagnetic radiation that imitates action of these irradiations on geostationary satellite orbit. After that, the comparative investigations of the changes in spectral reflectance and solar absorptance of these coatings were carried out.

Characterization of thin film solid oxide fuel-cell materials can be difficult due to the range of porosities in electrodes and electrolytes as well as the nano-sized pores and particles. In this study, optical characterization techniques such as ultraviolet–visible transmission and reflection spectrophotometry are illustrated as methods for achieving information about the film density from the film refractive index as well as the film thickness. These techniques were used to investigate the sintering process of colloidal CeO2 on sapphire substrates and polymeric precursor-derived ZrO2:16%Y (YSZ) thin films on silicon over the temperature range 400–1000 °C, and the results were compared with traditional characterization techniques such as electron microscopy, profilometry, ellipsometry, and x-ray diffraction line broadening analyses. Most of the techniques were in good agreement with the CeO2 grain size changing from 5–65 nm and the film thickness changing from 0.8–0.5 μm. Comparisons of transmission and reflection spectrophotometry with ellipsometry illustrated that scattering effects from the porous CeO2 films caused an overestimation of the refractive index from ellipsometry, but allowed for accurate grain size measurements from transmission and reflection data. Both techniques were in good agreement during the sintering of the YSZ thin films, with the density changing from 90–100% theoretical after heating between 400 and 800 °C.

Mg2+ binds to calmodulin without inducing the changes in secondary structure that are characteristic of Ca2+ binding, or the exposure of hydrophobic surfaces that are involved in typical Ca2+-dependent target interactions. The binding of Mg2+ does, however, produce significant spectroscopic changes in residues located in the Ca2+-binding loops, and the Mg-calmodulin complex is significantly different from apo-calmodulin in loop conformation. Direct measurement of Mg2+ binding constants, and the effects of Mg2+ on Ca2+ binding to calmodulin, are consistent with specific binding of Mg2+, in competition with Ca2+. Mg2+ increases the thermodynamic stability of calmodulin, and we conclude that under resting, nonstimulated conditions, cellular Mg2+ has a direct role in conferring stability on both domains of apo-calmodulin. Apo-calmodulin binds typical target sequences from skeletal muscle myosin light chain kinase and neuromodulin with Kd ∼ 70–90 nM (at low ionic strength). These affinities are virtually unchanged by 5 mM Mg2+, in marked contrast to the strong enhancement of peptide affinity induced by Ca2+. Under conditions of stimulation and increased [Ca2+], Mg2+ has a role in directing the mode of initial target binding preferentially to the C-domain of calmodulin, due to the opposite relative affinities for binding of Ca2+ and Mg2+ to the two domains. Mg2+ thus amplifies the intrinsic differences of the domains, in a target specific manner. It also contributes to setting the Ca2+ threshold for enzyme activation and increases the importance of a partially Ca2+-saturated calmodulin–target complex that can act as a regulatory kinetic and equilibrium intermediate in Ca2+-dependent target interactions.

Optical spectroscopy, including low and room temperature photoluminescence (PL), reflectance, PL measurements in high magnetic fields up to 12 T, and resonantly-enhanced electronic Raman scattering (RERS) in zero and high magnetic field, has been used to investigate exciton and impurity states and surface recombination in high quality heteroepitaxial GaN grown on sapphire and SiC. Theoretical finite-difference calculations of the donor states as a function of magnetic field have been carried out for comparison, including the effects of anisotropy in the effective mass and dielectric constant. Up to six residual donor species are observed in material grown by hydride vapor phase epitaxy (HVPE) and metalorganic chemical vapor deposition (MOCVD) from their n=2 and n=3 two-electron satellites observed in PL and by RERS. The donor-related nature of the relevant transitions is confirmed from their magnetic field dependence, and the spectral resolution is improved at high fields. The Si donor level is determined to have a binding energy of about 21 meV from observation of its two-electron satellite in lightly Si-doped HVPE material. The free exciton binding energy is shown to be about 26.4 meV, independent of strain, based on observations of the n=2 free exciton. The room temperature band-edge PL peak is confirmed to be free excitonic in nature, based on its linewidth and on comparison with simple reflectance measurements. Reflectance from the edge of a thick HVPE layer shows clear evidence of A, B, and C excitons obeying the relevant selection rules at both low and room temperature. Surface chemical treatments are shown to have substantial effects on room temperature PL efficiency. Passivation with ammonium or sodium sulfide solutions, in particular, yields increases in PL efficiency by a factor of five to seven over air-exposed surfaces. The passivation effect is stable in air, lasting at least one month.