A projection of ozone‐induced wheat production loss in China and India for the years 2000 and 2020 with exposure‐based and flux‐based approaches

Using a high‐resolution (40 × 40 km) chemical transport model coupled with the Regional Emission inventory in Asia (REAS), we simulated surface ozone concentrations ([O₃]) and evaluated O₃‐induced wheat production loss in China and India for the years 2000 and 2020 using dose–response functions based on AOT40 (accumulated [O₃] above 40 ppb) and POD_Y (phytotoxic O₃ dose, accumulated stomatal flux of O₃ above a threshold of Y nmol m^?2 s^?1). Two O₃ dose metrics (90 days AOT40 and POD₆) were derived from European experiments, and the other two (75 days AOT40 and POD₁₂) were adapted from Asian studies. Relative yield loss (RYL) of wheat in 2000 was estimated to be 6.4–14.9% for China and 8.2–22.3% for India. POD₆ predicted greater RYL, especially for the warm regions of India, whereas the 90 days AOT40 gave the lowest estimates. For the future projection, all the O₃ dose metrics gave comparable estimates of an increase in RYL from 2000 to 2020 in the range 8.1–9.4% and 5.4–7.7% for China and India, respectively. The lower projected increase in RYL for India may be due to conservative estimation of the emission increase in 2020. Sensitivity tests of the model showed that the POD_Y‐based estimates of RYL are highly sensitive to perturbations in the meteorological inputs, but that the estimated increase in RYL from 2000 to 2020 is much more robust. The projected increase in wheat production loss in China and India in the near future is substantially larger than the uncertainties in the estimation and indicates an urgent need for curbing the rapid increase in surface [O₃] in these regions.     

Interaction of drought and ozone exposure on isoprene emission from extensively cultivated poplar

The combined effects of ozone (O₃) and drought on isoprene emission were studied for the first time. Young hybrid poplars (clone 546, Populus deltoides cv. 55/56 x P. deltoides cv. Imperial) were exposed to O₃ (charcoal‐filtered air, CF, and non‐filtered air +40 ppb, E‐O₃) and soil water stress (well‐watered, WW, and mild drought, MD, one‐third irrigation) for 96 days. Consistent with light‐saturated photosynthesis (A_sat), intercellular CO₂ concentration (C_i) and chlorophyll content, isoprene emission depended on drought, O₃, leaf position and sampling time. Drought stimulated emission (+38.4%), and O₃ decreased it (?40.4%). Ozone increased the carbon cost per unit of isoprene emission. Ozone and drought effects were stronger in middle leaves (13th–15th from the apex) than in upper leaves (6th–8th). Only A_sat showed a significant interaction between O₃ and drought. When the responses were up‐scaled to the entire‐plant level, however, drought effects on total leaf area translated into around twice higher emission from WW plants in clean air than in E‐O₃. Our results suggest that direct effects on plant emission rates and changes in total leaf area may affect isoprene emission from intensively cultivated hybrid poplar under combined MD and O₃ exposure, with important feedbacks for air quality.     

White‐ and blue‐light‐emitting dysprosium(III) and terbium(III)‐doped gadolinium titanate phosphors

Here we report the synthesis and structural, morphological, and photoluminescence analysis of white‐ and blue‐light‐emitting Dy³⁺‐ and Tm³⁺‐doped Gd₂Ti₂O₇ nanophosphors. Single‐phase cubic Gd₂Ti₂O₇ nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy³⁺‐doped and ~50 nm for Tm³⁺‐doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy³⁺‐doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue‐light excitation. Intense blue light was obtained for Tm³⁺‐doped Gd₂Ti₂O₇ under UV excitation suggesting that this material could be used as a blue phosphor.     

Molten salt synthesis and luminescence of Dy3+‐doped Y3Al5O12 phosphors

Dy³⁺‐doped Y₃Al₅O₁₂ phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy³⁺‐doped Y₃Al₅O₁₂ phosphors was confirmed using X‐ray powder diffraction. Results indicated that Dy³⁺ doping did not change the Y₃Al₅O₁₂ phase. Following excitation at 352 nm, emission spectra of the Dy³⁺‐doped Y₃Al₅O₁₂ phosphors consisted of blue, yellow, and red emission bands. The influence of Dy³⁺ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy³⁺ doping concentration, due to changes in the structure around Dy³⁺. Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy³⁺‐doped Y₃Al₅O₁₂ phosphors.     

Elevated O3 concentrations alter the compartment-specific microbial communities inhabiting rust-infected poplars

Elevated ozone (O₃) can affect the susceptivity of plants to rust pathogens. However, the collective role of microbiomes involved in such interaction remains largely elusive. We exposed two cultivated poplar clones exhibiting differential O₃ sensitivities, to non-filtered ambient air (NF), NF + 40 ppb or NF + 60 ppb O₃-enriched air in field open-top chambers and then inoculated Melampsora larici-populina urediniospores to study their response to rust infection and to investigate how microbiomes inhabiting four compartments (phyllosphere, rhizosphere, root endosphere, bulk soil) are involved in this response. We found that hosts with higher O₃ sensitivity had significantly lower rust severity than hosts with lower sensitivity. Furthermore, the effect of increased O₃ on the diversity and composition of microbial communities was highly dependent on poplar compartments, with the microbial network complexity patterns being completely opposite between the two clones. Notably, microbial source analysis estimated that phyllosphere fungal communities predominately derived from root endosphere and vice versa, suggesting a potential transmission mechanism between plant above- and below-ground systems. These promising results suggest that further investigations are needed to better understand the interactions of abiotic and biotic stresses on plant performance and the role of the microbiome in driving these changes.     

Effect of Ga3+ and Gd3+ ions substitution on the structural and optical properties of Ce3+‐doped yttrium aluminium garnet phosphor nanopowders

The structural and optical properties of commercially obtained Y₃Al₅O₁₂:Ce³⁺ phosphor were investigated by replacing Al³⁺ with Ga³⁺ and Y³⁺ with Gd³⁺ in the Y₃Al₅O₁₂:Ce³⁺ structure to form Y₃(Al,Ga)₅O₁₂:Ce³⁺ and (Y,Gd)₃Al₅O₁₂:Ce³⁺. X‐Ray diffraction (XRD) results showed slight 2‐theta peak shifts to lower angles when Ga³⁺ was used and to higher angles when Gd³⁺ was used, with respect to peaks from Y₃Al₅O₁₂:Ce³⁺ and JCPDS card no. 73–1370. This could be attributed to induced crystal‐field effects due to the different ionic sizes of Ga³⁺ and Gd³⁺ compared with Al³⁺ and Y³⁺. The photoluminescence (PL) spectra showed broad excitation from 350 to 550 nm with a maximum at 472 nm, and broad emission bands from 500 to 650 nm, centred at 578 nm for Y₃Al₅O₁₂:Ce³⁺ arising from the 5d → 4f transition of Ce³⁺. PL revealed a blue shift for Ga³⁺ substitution and a red shift for Gd³⁺ substitution. UV–Vis showed two absorption peaks at 357 and 457 nm for Y₃Al₅O₁₂:Ce³⁺, with peaks shifting to 432 nm for Ga³⁺ and 460 nm for Gd³⁺ substitutions. Changes in the trap levels or in the depth and number of traps due to Ce³⁺ were analysed using thermoluminescence (TL) spectroscopy. This revealed the existence of shallow and deep traps. It was observed that Ga³⁺ substitution contributes to the shallowest traps at 74 °C and fewer deep traps at 163 °C, followed by Gd³⁺ with shallow traps at 87 °C and deep traps at 146 °C. Copyright © 2016 John Wiley & Sons, Ltd.     

Structural,morphological and steady state photoluminescence spectroscopy studies of red Eu3+‐doped Y2O3 nanophosphors prepared by the sol‐gel method

Europium trivalent (Eu³⁺)‐doped Y₂O₃ nanopowders of different concentrations (0.5, 2.5, 5 or 7 at.%) were synthesized by the sol‐gel method, at different pH values (pH 2, 5 or 8) and annealing temperatures (600°C, 800°C or 1000°C). The nanopowders samples were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared spectroscopy (FT‐IR) and steady state photoluminescence spectroscopy. The effect of pH of solution and annealing temperatures on structural, morphological and photoluminescence properties of Eu³⁺‐doped Y₂O₃ were studied and are discussed. It was found that the average crystallite size of the nanopowders increased with increasing pH and annealing temperature values. The Y₂O₃:Eu³⁺ material presented different morphology and its evolution depended on the pH value and the annealing temperature. Activation energies at different pH values were determined and are discussed. Under ultraviolet (UV) light excitation, Y₂O₃:Eu³⁺ showed narrow emission peaks corresponding to the ⁵D_0–⁷F_J (J = 0, 1, 2 and 3) transitions of the Eu³⁺ ion, with the most intense red emission at 611 assigned to forced electric dipole ⁵D₀→⁷F₂. The emission intensity became more intense with increasing annealing temperature and pH values, related to the improvement of crystalline quality. For the 1000°C annealing temperature, the emission intensity presented a maximum at pH 5 related to the uniform cubic‐shaped particles. It was found that for lower annealing temperatures (small crystallite size) the CTB (charge transfer band) position presented a red shift. Copyright © 2015 John Wiley & Sons, Ltd.     

Extraction of Y2O3:Cr3+ nanophosphor by eco‐friendly approach and its suitability for white light‐emitting diode applications

Cr³⁺‐doped Y₂O₃ (0.5–9 mol%) was synthesized by a simple solution combustion method using Aloe vera gel as a fuel/surfactant. The final obtained product was calcined at 750°C for 3 h, which is the lowest temperature reported so far for the synthesis of this compound. The calcined product was confirmed for its crystallinity and purity by powder X‐ray diffraction (PXRD) studies which showed a single‐phase nano cubic phosphor. The particles size estimated by Scherrer formula was in the range of 6–19 nm. The UV–vis spectra showed absorption bands at 198, 272 and 372 nm having band gap energy in the range 4.00–4.26 eV. In order to investigate the possibility of its use in white light emitting display applications, the photoluminescence properties of Cr³⁺‐doped Y₂O₃ nanophosphors were studied at an excitation wavelength in the near ultraviolet (UV) light region (361 nm). The emission spectra consisted of emission peaks in the blue (⁴F_9/2 → ⁶H_15/2), orange (⁴F_9/2 → ⁶H_13/2) and red (⁴F_9/2 → ⁶H_11/2) regions. The CIE coordinates (0.33, 0.33) lie in the white light region. Hence Y₂O₃:Cr³⁺ can be used for white light‐emitting diode (LED) applications.     

Luminescence properties of novel deep‐red‐emitting Ca3Al2Ge2O10:Cr3+ phosphors

Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphors were prepared by a high‐temperature solid‐state method, and their luminescence properties were investigated. Under excitation at 550 nm, Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphors exhibited a broad red emission band at 697 nm in the range 650–750 nm that was caused by the ²E→⁴A₂ transition of Cr³⁺. For the 697 nm emission peak, emission intensity reached a maximum at x = 0.07, and there was concentration quenching of Cr³⁺ in Ca₃Al₂Ge₂O₁₀; the corresponding concentration quenching mechanism was analysed. Under excitation at 262 nm, the Ca₃Al₂Ge₂O₁₀:Cr³⁺ phosphor showed a weakly broad emission band in the range 350–600 nm that was caused by intrinsic defects (V′′_Ca and V′′_O). Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of elevated ozone concentration on methane emission from a rice paddy in Yangtze River Delta,China

Few investigations have been made on the impact of elevated ozone (O₃) concentration on methane (CH₄) emission from rice paddies. Using open‐top chambers in situ with different O₃ treatments, CH₄ emissions were measured in a rice paddy in Yangtze River Delta, China in 2007 and 2008. There were four treatments applied: charcoal‐filtered air (CF), nonfiltered air (NF), and charcoal‐filtered air with different O₃ additions (O₃‐1 and O₃‐2). The mean O₃ concentrations during the O₃ fumigation were 19.7, 22.6, 69.6 and 118.6 ppb in 2007 and 7.0, 17.4, 82.2 and 138.3 ppb in 2008 for treatments CF, NF, O₃‐1 and O₃‐2, respectively. The rice yields, as compared with CF, were reduced by 32.8% and 37.1%, 58.3% and 52.1% in treatments O₃‐1 and O₃‐2 in 2007 and 2008, respectively. The diurnal patterns of CH₄ emission varied temporally with treatments and there was inconsistence in diurnal variations in CH₄ emissions from the paddy field. The daily mean CH₄ emissions were significantly lower in treatments O₃‐1 and O₃‐2 than those in treatments CF and NF. Compared with CF treatment, CH₄ emissions from the paddy field were decreased to 46.5% and 38.3%, 50.6% and 46.8% under treatments O₃‐1 and O₃‐2 in the whole growing seasons of 2007 and 2008, respectively. The seasonal mean CH₄ emissions were negatively related with AOT40 (accumulative O₃ concentration above 40 ppb; P < 0.01 in both years), but positively related to the relative rice yield (reference to CF; P < 0.01 in 2007 and P < 0.001 in 2008), aboveground biomass (P < 0.01 in both years) and underground biomass (P < 0.01 in 2007 and P < 0.05 in 2008). The decreased CH₄ emission from the rice paddy due to an increased O₃ exposure might partially mitigate the global warming potential induced by soil carbon loss under elevated O₃ concentrations.     

Improving green emission of Tb3+ ions in BaO‐B2O3‐P2O5 glasses by means of Al3+ ions

BaO‐B₂O₃‐P₂O₅ glasses doped with a fixed concentration of Tb³⁺ ions and varying concentrations of Al₂O₃ were synthesized, and the influence of the Al³⁺ ion concentration on the luminescence efficiency of the green emission of Tb³⁺ ions was investigated. The optical absorption, excitation, luminescence spectra and fluorescence decay curves of these glasses were recorded at ambient temperature. The emission spectra of terbium ions when excited at 393 nm exhibited two main groups of bands, corresponding to ⁵D₃ → ⁷F_j (blue region) and ⁵D₄ → 7F_j (green region). From these spectra, the radiative parameters, viz., spontaneous emission probability A, total emission probability A_T, radiative lifetime τ and fluorescent branching ratio β, of different transitions originating from the ⁵D₄ level of Tb³⁺ ions were evaluated based on the Judd‐Ofelt theory. A clear increase in the quantum efficiency and luminescence of the green emission of Tb³⁺ ions corresponding to ⁵D₄ → ⁷F₅ transition is observed with increases in the concentration of Al₂O₃ up to 3.0 mol%. The improvement in emission is attributed to the de‐clustering of terbium ions by Al³⁺ ions and also to the possible admixing of wave functions of opposite parities. Copyright © 2016 John Wiley & Sons, Ltd.     

Crystal structure and luminescence properties of the blue‐green‐emitting Ba9(Lu,Y)2Si6O24:Ce3+ phosphor

Samples of the Ba₉(Lu_2‐xY_x)Si₆O₂₄:Ce³⁺ (x = 0–2) blue‐green phosphors were synthesized by solid‐state reactions. All the samples exhibited a rhombohedral crystal structure. As the Y³⁺ concentration increased, the diffraction peaks shifted to the small angle region and the lattice parameters increased due to the larger ionic radius of Y³⁺ (r = 0.900 Å) compared with that of Lu³⁺ (r = 0.861 Å). Under 400 nm excitation, samples exhibited strong blue‐green emissions around 490 nm. The emission bands had a slight blue shift that resulted from weak crystal‐field splitting with increasing Y³⁺ concentration. Luminescence intensity and quantum efficiency (QE) decreased with increasing Y³⁺ concentration. The internal QE decreased from 74 to 50% and the external QE decreased from 50 to 34% as x increased from 0 to 2. The thermal stability of the Lu series was better than that of the Y‐series. The excitation band peak around 400 nm matched well with the emission light from the efficient near‐ultraviolet (NUV) chip. These results indicate promising applications for these NUV‐based white light‐emitting diodes.     

Contribution of volatile organic compound fluxes to the ecosystem carbon budget of a poplar short‐rotation plantation

Biogenic volatile organic compounds (BVOCs) are major precursors of both ozone and secondary organic aerosols (SOA) in the troposphere and represent a non‐negligible portion of the carbon fixed by primary producers, but long‐term ecosystem‐scale measurements of their exchanges with the atmosphere are lacking. In this study, the fluxes of 46 ions corresponding to 36 BVOCs were continuously monitored along with the exchanges of mass (carbon dioxide and water vapor) and energy (sensible and latent heat) for an entire year in a poplar (Populus) short‐rotation crop (SRC), using the eddy covariance methodology. BVOC emissions mainly consisted of isoprene, acetic acid, and methanol. Total net BVOC emissions were 19.20 kg C ha^?1 yr^?1, which represented 0.63% of the net ecosystem exchange (NEE), resulting from ?23.59 Mg C ha^?1 yr^?1 fixed as CO₂ and 20.55 Mg C ha^?1 yr^?1 respired as CO₂ from the ecosystem. Isoprene emissions represented 0.293% of NEE, being emitted at a ratio of 1 : 1709 mol isoprene per mol of CO₂ fixed. Based on annual ecosystem‐scale measurements, this study quantified for the first time that BVOC carbon emissions were lower than previously estimated in other studies (0.5–2% of NEE) on poplar trees. Furthermore, the seasonal and diurnal emission patterns of isoprene, methanol, and other BVOCs provided a better interpretation of the relationships with ecosystem CO₂ and water vapor fluxes, with air temperature, vapor pressure deficit, and photosynthetic photon flux density.     

Structural and optical properties of europium‐ and titanium‐doped Y2O3 nanoparticles

Luminescent nanoparticles of Y₂O₃ doped with europium (Eu) and/or titanium (Ti) were synthesized using modified sol–gel routes. The crystalline cubic phase was confirmed using X‐ray powder diffraction (XRD). Particle morphology and size were evaluated using scanning and transmission electron microscopy. High‐resolution transmission electron microscopy showed that the synthesis method affected the average particle size and the Fourier transform of the images showed the lattice plane distances, indicating that the samples presented high crystallinity degree in accordance with the XRD pattern. The Ti valence was investigated using X‐ray absorption near edge spectroscopy and the tetravalent form was the dominant oxidizing state in the samples, mainly in Eu and Ti co‐doped Y₂O₃. Optical behaviour was investigated through X‐ray excited optical luminescence and photoluminescence under ultraviolet–visible (UV–vis) and vacuum ultraviolet (VUV) excitation. Results indicated that Eu³⁺ is the emitting centre in samples doped with only Eu and with both Eu and Ti with the ⁵D₀→⁷F₂ transition as the most intense, indicating Eu³⁺ in a noncentrosymmetric site. Finally, in the Eu,Ti‐doped Y₂O₃ system, Ti³⁺ (or Ti^IV) excitation was observed but no Ti emission was present, indicating a very efficient energy transfer process from Ti to Eu³⁺. These results can aid the development of efficient nanomaterials, activated using UV, VUV, or X‐rays.     

Spectral‐converting study of Ba9–3(m+n)/2ErmYbnY2Si6O24 (m = 0.005 – 0.2, n = 0 – 0.3) orthosilicate phosphors

Optical materials composed of Ba_9–3(m+n)/2Er_mYb_nY₂Si₆O₂₄ (m = 0.005–0.2, n = 0–0.3) were prepared using a solid‐state reaction. The X‐ray diffraction patterns of the obtained phosphors were examined to index the peak positions. The photoluminescence (PL) excitation and emission spectra of the Er³⁺‐activated phosphors and the critical emission quenching as a function of Er³⁺ content in the Ba_9–3m/2Er_mY₂Si₆O₂₄ structure were monitored. The spectral conversion properties of Er³⁺ and Er³⁺–Yb³⁺ ions doped in Ba₉Y₂Si₆O₂₄ phosphors were elucidated under diode‐laser irradiation at 980 nm. Up‐conversion emission spectra and the dependence of the emission intensity on pump power for the Ba_8.55Er_0.1Yb_0.2Y₂Si₆O₂₄ phosphor were investigated. The desired up‐conversion of the emitted light, which passed through the green, yellow, orange and red regions of the spectrum, was achieved through the use of appropriate Er³⁺ and/or Yb³⁺ concentrations in the host structure and 980 nm excitation light. The up‐conversion mechanism in the phosphors is described by an energy‐level schematic. Copyright © 2015 John Wiley & Sons, Ltd.     

Optical characterization and the energy level scheme for Ce3+‐doped BaY2Si3O10 blue‐emitting phosphor

A series of Ce³⁺‐activated blue‐emitting phosphors BaY₂Si₃O₁₀ (BYSO) was designed and synthesized by a conventional solid‐state method. Upon ultraviolet light (250–370 nm) excitation, the obtained phosphors showed an intense blue emission band centered at 400–427 nm depending on doping concentration, and corresponding to the 5d→4f transition of Ce³⁺. The effects of doping concentration on crystal structure, emitting color, photoluminescence and photoluminescence excitation spectra, as well as the concentration quenching mechanism were studied in detail. The optimal doping concentration of Ce³⁺ in this phosphor was demonstrated to be about 0.75% and the concentration quenching mechanism can be ascribed to electric dipole–dipole interactions with a critical distance of ~38 Å. These fine luminescence properties indicate that BYSO:Ce³⁺ may be a potential blue phosphor for full‐color ultra‐violet (UV) white light emitting diodes (WLEDs).     

Synthesis and photoluminescence characteristics of Sm3+‐doped Bi4Si3O12 red‐emitting phosphor

A series of novel red‐emitting Sm³⁺‐doped bismuth silicate phosphors, Bi₄Si₃O₁₂:xSm³⁺ (0.01 ≤ x ≤ 0.06), were prepared via the sol–gel route. The phase of the synthesized samples calcinated at 800 °C is isostructural with Bi₄Si₃O₁₂ according to X‐ray diffraction results. Under excitation with 405 nm light, some typical peaks of Sm³⁺ ions centered at 566, 609, 655 and 715 nm are found in the emission spectra of the Sm³⁺‐doped Bi₄Si₃O₁₂ phosphors. The strongest peak located at 609 nm is due to ⁴G_5/2–⁶H_7/2 transition of Sm³⁺. The luminescence intensity reaches its maximum value when the Sm³⁺ ion content is 4 mol%. The results suggest that Bi₄Si₃O₁₂:Sm³⁺ may be a potential red phosphor for white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.     

Mechanoluminescence,thermoluminescence, photoluminescence studies on Ca3Y2Si3O12:RE3+ (RE3+ = Dy3+and Eu3+) phosphors

Dy³⁺ and Eu³⁺ activated Ca₃Y₂Si₃O₁₂ phosphors were synthesized by the solid‐state synthesis method. The phosphors were characterized by X‐ray diffraction (XRD), mechanoluminescence (ML), thermoluminescence (TL) and photoluminescence (PL) to determine structure and luminescence. For ML glow curves, only one peak was observed, as only one type of luminescence centre was formed during irradiation. The Ca₃Y₂Si₃O₁₂:Dy³⁺ TL glow curve showed a single peak at 151.55°C and the Ca₃Y₂Si₃O₁₂:Eu³⁺ TL glow curve peaked at 323°C with a small peak at 192°C, indicating that two types of traps were activated. The trapping parameters for both the samples were calculated using Chen's peak shape method. Dy³⁺‐activated Ca₃Y₂Si₃O₁₂ showed emission at 482 and 574 nm when excited by a 351 nm excitation wavelength, whereas the Eu³⁺‐activated Ca₃Y₂Si₃O₁₂ phosphor PL emission spectra showed emission peaks at 613 nm, 591 nm, 580 nm when excited at 395 nm wavelength. When excited at 466 nm, prominent emission peaks were observed at their respective positions with very slight shifts. Copyright © 2015 John Wiley & Sons, Ltd.     

Sodium Storage and Transport Properties in Layered Na2Ti3O7 for Room‐Temperature Sodium‐Ion Batteries

Layered sodium titanium oxide, Na₂Ti₃O₇, is synthesized by a solid‐state reaction method as a potential anode for sodium‐ion batteries. Through optimization of the electrolyte and binder, the microsized Na₂Ti₃O₇ electrode delivers a reversible capacity of 188 mA h g^?1 in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0–3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na⁺/Na, in good agreement with a first‐principles prediction of 0.35 V. The Na storage properties in Na₂Ti₃O₇ are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na₂Ti₃O₇ exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid‐state interphase layer on Na₂Ti₃O₇ electrode is analyzed. A zero‐current overpotential related to thermodynamic factors is observed for both nano‐ and microsized Na₂Ti₃O₇. The electronic structure, Na⁺ ion transport and conductivity are investigated by the combination of first‐principles calculation and electrochemical characterizations. On the basis of the vacancy‐hopping mechanism, a quasi‐3D energy favorable trajectory is proposed for Na₂Ti₃O₇. The Na⁺ ions diffuse between the TiO₆ octahedron layers with pretty low activation energy of 0.186 eV.     

Comparison of crop yield sensitivity to ozone between open‐top chamber and free‐air experiments

Assessments of the impacts of ozone (O₃) on regional and global food production are currently based on results from experiments using open‐top chambers (OTCs). However, there are concerns that these impact estimates might be biased due to the environmental artifacts imposed by this enclosure system. In this study, we collated O₃ exposure and yield data for three major crop species—wheat, rice, and soybean—for which O₃ experiments have been conducted with OTCs as well as the ecologically more realistic free‐air O₃ elevation (O₃‐FACE) exposure system; both within the same cultivation region and country. For all three crops, we found that the sensitivity of crop yield to the O₃ metric AOT40 (accumulated hourly O₃ exposure above a cut‐off threshold concentration of 40 ppb) significantly differed between OTC and O₃‐FACE experiments. In wheat and rice, O₃ sensitivity was higher in O₃‐FACE than OTC experiments, while the opposite was the case for soybean. In all three crops, these differences could be linked to factors influencing stomatal conductance (manipulation of water inputs, passive chamber warming, and cultivar differences in gas exchange). Our study thus highlights the importance of accounting for factors that control stomatal O₃ flux when applying experimental data to assess O₃ impacts on crops at large spatial scales.