Stable Cesium Research Articles

Fabrication of Highly Stable Fully-Inorganic Halide Perovskite Films for Optoelectronic Application.

Despite the fact that stability is a critical issue affecting halide perovskite after the materials have been developed, these materials continue to be studied due to their outstanding optoelectronic characteristics such as narrow emission band width, high PLQY. Many methods are suggested and improved, but the limitations for the display and lighting applications are still remaining. Here, we propose the fabrication of stable cesium lead tri-halide (CsPbX₃; X= Cl, Br, I) perovskite films using photocurable polyurethane material, norland optical adhesive 63 (NOA 63), to generate white LEDs by placing films on the InGaN 450 nm blue chip. Comparing with the conventional perovskites, fabricated films well maintained the luminescence properties such as full widths at half maximum (FWHM) of 18 nm and 31 nm for green and red films, respectively. For the stability issue, pristine perovskite without encapsulation is decomposed immediately at high humidity and temperature, but NOA 63 encapsulated perovskite maintained a PL emission property of 60% after four hours in artificial atmosphere. The CIE color triangle reached ~119% of the NTSC standard, exhibiting high color purity. From the results, we confirm that the NOA 63 encapsulated halide perovskites are beneficial when applied in optoelectronic applications due to their improved stability and maintained characteristics.

Unraveling the Impact of Halide Mixing on Crystallization and Phase Evolution in CsPbX3 Perovskite Solar Cells

Summary All-inorganic perovskite solar cells (PSCs) have attracted wide attention for their excellent thermal stability. However, the detailed crystallization process and complicated phase-transition mechanism of the CsPbX3 film with different halide compositions (I, Br, Cl) remain mysterious. In this study, systematic investigations are performed via state-of-art in situ grazing-incidence wide-angle X-ray scattering to understand the role of the halide elements in all-inorganic perovskite crystallization kinetics, phase-transition, and stabilization mechanism as well as how film morphology and grain size are affected. Based on these results, we were able to fabricate high-performance ternary halide (I, Br, Cl) all-inorganic PSCs through a precise compositional engineering. Our results provide guidance for an in-depth understanding of all-inorganic perovskite materials and pave the way to obtain high-performance all-inorganic PSCs.

Evidence of superoxide-like CsO2 formation on a cesiated model surface

The investigation of light atoms and molecules interaction on cesiated surfaces attracted remarkable attention during the last years, mainly due to its application on tuning the operating conditions of negative ion sources for fusion devices. The commonly suboptimal vacuum level in such facilities makes the process prone to contamination by impurities and, particularly, by oxygen. In the present study, we investigate the interaction of molecular oxygen on a surface slab of molybdenum with medium Cs coverage. Plane Wave (PW) based DFT and ab initio molecular dynamics calculations on this system revealed strong chemisorption of oxygen species toward Cs atoms on the surface. The binding energies for molecular oxygen calculated at DFT level, range between 0.5 eV and 2.0 eV, depending on the impact site on the surface and interaction orientation, thus confirming a strong bound state at surface. The adsorbed O2 molecule was further stabilized over the slab by constrained and free first-neighbours PW molecular dynamics of the oxygen molecule on the proximity of Cs atoms. As a result, a stable caesium oxide structure was found on the surface, and, from an accurate multi-property analysis, we have found that its geometrical and electronic features strongly resemble those typical of a CsO2 superoxide compound.

Solar cell using spray casted Cs2SnI6 perovskite thin films on chemical bath deposited CdS yielding high open circuit voltage

In the present work, we report synthesis of Cs2SnI6 double perovskite films by direct spray casting of precursor containing CsI and SnI2 dissolutions in DMF and the fabrication of solar cells using these films as absorber material. The films were prepared by varying the CsI: SnI2 molar ratio in the precursor, 2:1, 1:1, 1:2, 1:3 and 1:4. X-ray diffraction and Raman spectral analysis showed the formation of Cs2SnI6 films with cubic structure when the precursor solution contained excess tin iodide. The optical band gap value of the films was ~1.2–1.3 eV and the films were photoconductive. The stability studies established that the perovskite films were stable under ambient exposure. Further, we fabricated all-inorganic photovoltaic structures Glass/FTO/CdS/Cs2SnI6/C/Ag, using Cs2SnI6 films formed at different conditions as absorber layer. Post thermal annealing of the PV devices at 150 °C showed the highest Voc = 0.86 V for this material. Thus, our results have demonstrated that spray deposition is a reproducible method to synthesize stable cesium tin iodide perovskite for applications in all inorganic p-n junction solar cells and other optoelectronic devices.

Tracing radioactive cesium in stem wood of three Japanese conifer species 3\xa0years after the Fukushima Dai-ichi Nuclear Power Plant accident

To understand the dynamics of accident-derived radioactive cesium (137Cs) in stem wood that had a substantial amount of heartwood at the time of the Fukushima Dai-ichi Nuclear Power Plant accident, the radial and vertical distributions of 137Cs activity concentration in stem wood of Japanese cedar (Cryptomeria japonica), cypress (Chamaecyparis obtusa), and larch (Larix kaempferi) were investigated. In addition, the natural distribution of stable cesium (133Cs), rubidium (85Rb), and potassium (39K) concentrations was analyzed to determine the characteristics of 137Cs distribution. Wood disks were collected from the tree stems of six cedars, three cypresses, and two larches at multiple heights in 2014, and the concentrations were measured every 2 cm in the radial direction. 137Cs distribution in stem wood differed among tree species, sampling site, and vertical position of the stem within a tree. Statistical analyses suggested that the radial distribution of 137Cs within the heartwood can be explained by the heartwood moisture content and the distance from the treetop, regardless of species, while the distribution between sapwood and heartwood was dependent on the heartwood cross-sectional area and was additionally different between larch and other species. Similarly, the heartwood/sapwood concentration ratios of stable alkali metals differed between larch and the other species. In the larch, the ratio was ca. 0.5 for all elements, but the ratio was over 1.0 and differed among elements in the other species. Consequently, the species-specific difference in the distribution of 137Cs between sapwood and heartwood was considered to be due to different activity levels of radial transport toward the heartwood. The radial variation pattern of the 137Cs/133Cs concentration ratio showed that less 137Cs was transferred to the inner heartwood compared with the 133Cs distribution pattern in many trees; however, there was also a tree in which 137Cs was excessively transferred to the inner heartwood compared with the 133Cs distribution pattern. Such patterns may result from a combination of significant foliar uptake of 137Cs and poor root uptake after the accident, in addition to the high moisture content of the heartwood.

Highly luminescent and stable lead-free cesium copper halide perovskite powders for UV-pumped phosphor-converted light-emitting diodes

Lead halide perovskites have drawn extensive attention over recent decades owing to their outstanding photoelectric performances. However, their toxicity and instability are big issues that need to be solved for further commercialization. Herein, we adopt a facile dry ball milling method to synthesize lead-free Cs 3 Cu 2 X 5 ( X = I , Cl) perovskites with photoluminescence (PL) quantum yield up to 60%. The optical features including broad emission spectrum, large Stokes shift, and long PL lifetime can be attributed to self-trapped exciton recombination. The as-synthesized blue emissive Cs 3 Cu 2 I 5 and green emissive Cs 3 Cu 2 Cl 5 lead-free perovskite powders have good thermal stability and photostability. Furthermore, UV-pumped phosphor-converted light-emitting diodes were obtained by using Cs 3 Cu 2 I 5 and Cs 3 Cu 2 Cl 5 as phosphors.

Estimation of water seepage rate in the active crater lake system of Kusatsu-Shirane volcano, Japan, using FDNPP-derived radioactive cesium as a hydrological tracer

We describe here a first attempt to estimate the water seepage rate of an active crater lake using radioactive cesium dispersed into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011 as a hydrological tracer. Kusatsu-Shirane volcano is one of the most active volcanoes in Japan and has an active crater lake named Yugama. There is no outflow such as a river from Yugama crater lake. The content level of stable cesium (133Cs) in Yugama water was almost constant at 15–20 nM during the sampling period of Nov. 2011 to Nov. 2014. In contrast to 133Cs, however, the radioactive cesium (134Cs and 137Cs) concentrations in Yugama water decreased at a more rapid rate than expected by radioactive decay. Based on the decreasing rates of activity concentrations of 134Cs and 137Cs in Yugama water during the three years between 2012 and 2014, it is estimated that 700–800 m3 of the Yugama water, which corresponds approximately to 0.1% of the total volume, leaks through the lakebed per day. In the estimation, balance between leakage of radioactive cesium contaminated water though lake bed and geothermal inflow of radioactive cesium-free water in the volcano was taken into account. Consequently, the water seepage rate of the Yugama crater lake was calculated to be 8.1–9.3 L s−1.

Correction: Highly stable hetero-structured green-emitting cesium lead bromide nanocrystals via ligand-mediated phase control.

Correction for 'Highly stable hetero-structured green-emitting cesium lead bromide nanocrystals via ligand-mediated phase control' by G. Krishnamurthy Grandhi et al., Nanoscale, 2019, 11, 21137-21146.

Solid-state synthesis of stable and color tunable cesium lead halide perovskite nanocrystals and the mechanism of high-performance photodetection in a monolayer MoS2/CsPbBr3 vertical heterojunction

Color tunable cesium lead halide perovskite nanocrystals with high stability and the mechanism of high-performance photodetection in a monolayer MoS2/CsPbBr3 vertical heterojunction.

Crystalline phase-controlled synthesis of regular and stable endotaxial cesium lead halide nanocrystals

The effects of precursors on the perovskite nanocrystals based on APTES base ligands were investigated and discussed.

Draft genome sequence and nomenclature adjustment of Rhodococcus qingshengii CS98, a cesium-accumulating strain isolated in Japan

Strains within the Rhodococcus genus have the ability to endure a range of recalcitrant compounds and metabolise a variety of pollutants. As a result there is increasing interest in these robust prokaryotes for their applications in bioremediation of contaminated environments and bioconversion of industrial wastes. In this announcement we present the draft genome sequence of R. qingshengii CS98, a soil isolate from Japan with the demonstrated ability to accumulate both stable and radioactive caesium.

Could 137Cs remediation be accomplished with stable cesium (CsCl) on tropical soils?

Stable cesium can be considered as the best element for desorption of soil radio-cesium. It is considered an element that slightly absorbed by plants, so that the application of high doses to the soil could increase the absorption of 137Cs, which is desired for the remediation of contaminated soils. There is shortage of knowledge on remediation of tropical and subtropical soils contaminated with 137Cs. The aim of this work was to evaluate the use of 133Cs for the remediation of Brazilian tropical and subtropical soils contaminated with 137Cs. In addition, we investigated the Cs uptake by bean plants (Phaseolus vulgaris L.) grown in Cs contaminated soil. The experiment was carried out in pots under greenhouse conditions. Seven soil types were used in the experiment (Oxisol, Udox, Psamment, Ochrept; Aquoll; Udox and Udult), which received the application of four doses of 133Cs (0, 5, 10 and 20 mg/pot in a completely randomized design arranged in a factorial scheme (7 soil types x 4 doses of 133Cs) with three replicates. An increase in transfer factor values of 137Cs was observed for both shoot growth and grains, as well as in percentage of total activity of 137Cs removed from the soil regarding to addition of stable cesium levels in all soils. The results showed that psamment soil presented higher specific activity of 137Cs in the soil and grains, as well as for the transfer coefficient from soil to shoot growth and grains. The application of stable cesium chloride to soil did not cause any effects on dry matter production of shoot growth and grains. The addition of 133Cs increased the transfer from soil 137Cs to the plant regardless of soil type, proving the efficiency of this practice for the remediation of soils contaminated with radioactive Cs. In addition, the plants of common bean were efficient for use in phytoremediation.

Efficient sampling of shiitake-inoculated oak logs to determine the log-to-mushroom transfer factor of stable cesium.

BackgroundStable cesium (133Cs) naturally exists in the environment whereas recently deposited radionuclides (e.g., 137Cs) are not at equilibrium. Stable cesium has been used to understand the long-term behavior of radionuclides in plants, trees and mushrooms. We are interested in using 133Cs to predict the future transfer factor (TF) of radiocesium from contaminated logs to shiitake mushrooms in Eastern Japan. However, the current methodology to obtain a representative wood sample for 133Cs analysis involves mechanically breaking and milling the entire log (excluding bark) to a powder prior to analysis. In the current study, we investigated if sawdust obtained from cutting a log along its length at eight points is as robust but a faster alternative to provide a representative wood sample to determine the TF of 133Cs between logs and shiitake.MethodsOak logs with ready-to-harvest shiitake fruiting bodies were cut into nine 10-cm discs and each disc was separated into bark, sapwood and heartwood and the concentration of 133Cs was measured in the bark, sapwood, heartwood, sawdust (generated from cutting each disc) and fruiting bodies (collected separately from each disc), and the wood-to-shiitake TF was calculated.ResultsWe found that the sawdust-to-shiitake TF of 133Cs did not differ (P = 0.223) compared to either the sapwood-to-shiitake TF or heartwood-to-shiitake TF, but bark did have a higher concentration of 133Cs (P < 0.05) compared to sapwood and heartwood. Stable cesium concentration in sawdust and fruiting bodies collected along the length of the logs did not differ (P > 0.05).DiscussionSawdust can be used as an alternative to determine the log-to-shiitake TF of 133Cs. To satisfy the goals of different studies and professionals, we have described two sampling methodologies (Methods I and II) in this paper. In Method I, a composite of eight sawdust samples collected from a log can be used to provide a representative whole-log sample (i.e., wood and bark), whereas Method II allows for the simultaneous sampling of two sets of sawdust samples—one set representing the whole log and the other representing wood only. Both methodologies can greatly reduce the time required for sample collection and preparation.

Uptake and elemental distribution of radiosilver 108mAg and radiocesium 137Cs in shiitake mushrooms (Lentinula edodes)

The bioconcentration factors for radiosilver (108mAg) and radiocesium (137Cs) for shiitake mushrooms from an artificially contaminated sawdust substrate were found to be 0.11 and 3.8, respectively. The main fraction of radiosilver was found in the stalk rather than the cap, whereas radiocesium accumulated mostly in the cap of the shiitake mushroom. The location of radiocesium inside the cap was analyzed by autoradiography, and the location of stable silver by LA-ICP-MS imaging. Furthermore, a method for semi-quantification of stable silver and cesium for organic solid samples was developed as an addition to the mostly qualitative autoradiography.

Potential of the submerged plant Myriophyllum spicatum for treatment of aquatic environments contaminated with stable or radioactive cobalt and cesium

Modern technological routes of decontamination of polluted environments are expected to outperform traditional strategies. Such routes have been perceived as more efficient and/or less expensive, and, most of all, as environmentally friendly. In this context, submerged plants without any agricultural use are considered new and intriguing alternatives in the current search for more sustainable remediation of toxic and radioactive wastewater.Myriophyllum spicatum (Eurasian watermilfoil), a submerged aquatic plant present in fresh water streams, is considered a threat for aquatic environment. In present research, this plant was utilized for decontamination of simulated wastewater spiked with both radioactive and non-radioactive cobalt and cesium isotopes. Several parameters were evaluated to optimize the phytoremediation of these elements, such as the pH-value of the contaminated medium, illumination, contact time, ion competition, concentration of dissolved elements, mass of plant, and content of radioactive material. More than 90% and 60% of stable cobalt and cesium, respectively, were eliminated at optimal conditions of contact time with higher pH-value, light, and optimum mass of applied biomass. The same elimination values were achieved also in case of using radioisotopes of the same elements. The study demonstrates that Myriophyllum spicatum can be used as a promising candidate for phytoremediation of cobalt and cesium even if present as radioisotopes from contaminated aqueous media, thus being a green alternative for traditional remediation technologies.

Response of Plantago major to cesium and strontium in hydroponics: Absorption and effects on morphology, physiology and photosynthesis

Human activities lead to increasing concentration of the stable elements cesium (Cs) and strontium (Sr) and their radioactive isotopes in the food chain, where plants play an important part. Here we investigated Plantago major under the influence of long-term exposure to stable Cs and Sr.The plants were cultivated hydroponically in different concentrations of cesium sulfate (between 0.002 and 20 mM) and strontium nitrate (between 0.001 and 100 mM).Uptake of Cs and Sr into leaves was analyzed from extracts by inductively coupled plasma mass spectrometry (ICP-MS). It was increased with increasing external Cs and Sr concentrations. However, the efficiency of Cs and Sr transfer from solution to plants was higher for low external concentrations. Highest transfer factors were 6.78 for Cs and 71.13 for Sr. Accumulation of Sr was accompanied by a slight decrease of potassium (K) and calcium (Ca) in leaves, whereas the presence of Cs in the medium affected only uptake of K.The toxic effects of Cs and Sr were estimated from photosynthetic reactions and plant growth.In leaves, Cs and Sr affected the chlorophyll fluorescence even at their low concentrations. Low and high concentrations of both ions reduced dry weight and length of roots and leaves.The distribution of the elements between the different tissues of leaves and roots was investigated using Energy Dispersive X-Ray microanalysis (EDX) with scanning electron microscope (SEM). Overall, observations suggested differential patterns in accumulating Cs and Sr within the roots and leaves.When present in higher concentrations the amount of Cs and Sr transferred from environment to plants was sufficient to affect some physiological processes. The experimental model showed a potential for P. major to study the influence of radioactive contaminants and their removal from hotspots.

Combination of coprecipitation and foam separation processes for rapid recovery and preconcentration of cesium radionuclides from water systems

Foam separation of 137Cs+ radionuclides coprecipitated with cadmium(II) hexacyanoferrate (137Cs-CdHCF) particles is investigated in this study using two types of surfactants. The effects of several coprecipitation and foam separation parameters on the recovery percentage and volume reduction of cesium radionuclides are evaluated. The cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA), and the anionic one, sodium lauryl sulfate (NaLS), had the ability to float 137Cs-CdHCF particles at [Cd(II)]/[KHCF] molar ratios of 0.5 and 2, respectively. Recovery percentages of 92% and 88% are obtained in the pH range of 4.7–8.3 and 3.8–9.5 using HDTMA and NaLS, respectively. The addition of stable cesium during the coprecipitation process improved the recovery percentage (98% for HDTMA and 96% for NaLS). The recovery process is very fast where induction time of <15min (for coprecipitation process) and <5min (for foam separation process) are sufficient for efficient recovery of cesium radionuclides. The proposed strategy succeeded to efficiently preconcentrate cesium radionuclides from surface water where recovery percentage more than 99% with high volume reduction is achieved using HDTMA. Comparison of the present combined process with previously reported preconcentration processes proved its applicability for preconcentration of cesium radionuclides from water systems.

Long-term cycling of 137Cs in Pinus Kesiya at Wat Chan Thailand

Surface soil and above-ground parts of Pinus kesiya (Three-needled pine) were collected at Wat Chan pine forest to study cycling of 137Cs. Cs-137 derived from nuclear weapons tests up to 1963 was found to have accumulated at a shallow depth (<5 cm) in the forest soil. Calculated total deposition of 137Cs was in the range of previous studies and could be used as a reference for nuclear test deposition of 137Cs fallout in northern Thailand and nearby locations. Potassium in soil does not appear to be a good indicator for long-term radiocaesium cycling. Finally, ‘available’ stable caesium (133Cs) in the soil was found to be an appropriate indicator for studying uptake of 137Cs by Pinus kesiya at Wat Chan.

In-situ oxidation effect on pore size distribution in investigating adsorption properties under various geochemical conditions

Redox affected pumice tuff was used to investigate the changes of pore properties due to oxidation and its possible consequences to adsorption of nuclides on it. Porosity and pore size distribution were analyzed by mercury injection technique and scanning electron microscopy. Batch experiment was carried out with 1 cm3 block shaped intact pumice tuff samples to determine adsorption coefficient, Kd at several pH, ionic strength and initial nuclide concentrations of stable cesium (133Cs). Pore area, surface area and specific surface area were determined from pore size distribution data before and after adsorption experiment and later compared between fresh and oxidized samples. The results showed that reduction of less than 0.33 μm size micro pores due to oxidation is mainly responsible for reducing surface areas, eventually reducing the sorption quantity. Influence of pore properties became negligible in redox affected pumice tuff indicating inverse relation of oxidation phenomena with adsorption coefficients values.

Correlation between Different Type of Caesium Carrier in The Radiocaesium Interception Potential Measurement for Forest Soils

Radiocaesium, especially 137Cs, is one of major heavy fission product radionuclide that has a relatively long half-life and acts as a dangerous persistent pollutant to the environment. It could be dispersed widely through the atmosphere during nuclear weapon test and reactor accident such as Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) disaster in Japan. High retention of radiocaesium in the surface of forest floor surrounding Fukushima area is important issues to measure further potential risk of health and environment contamination. Radiocaesium Interception Potential (RIP) values are related to the sorption capacity of radioactive Cs in clay minerals, and in this study, we investigated the correlation between different type of Cs carrier to the RIP and their adsorption character in soil. The RIP values of all soil sample were varied from 27.27 to 522.66 mmol kg-1. The carrier effect on RIP was conducted using carrier 134Cs, carrier-free that contains 134Cs, 136Cs and 137Cs and 133Cs stable isotopes. Correlation between different type of carrier suggests a relatively lower RIP for stable caesium as a carrier. This phenomena could be caused by competitive adsorption among of caesium ions in the frayed edge sites of soil mineral. Organic carbon content and CEC also contributed to the RIP value. No significant difference found of C/N ratio and CEC values between deciduous and coniferous forest soil as they also have similarity of mineral content in soil.