Elemental Composition Analysis Research Articles

The formed surface characteristics of SiCf/SiC composite in the nanosecond pulsed laser ablation

For the advantages of high-temperature resistance, corrosion resistance and ultra-high hardness, SiCf/SiC composite is becoming a preferred material for manufacturing aero-engine parts. However, the anisotropy and heterogeneity bring great challenges to the processing technology. In this study, a nanosecond pulsed laser is applied to process SiCf/SiC composite, where the influence of the scanning speed and laser scanning direction to the SiC fibers on the morphology of ablated grooves is investigated. The surface characteristics after ablation and the involved chemical reaction of SiCf/SiC are explored. The results show that the increased laser scanning speed, accompanied by the decreasing spot overlap rate, leads to the less accumulation of energy on the material surface, so the ablation effect drops. In addition, for the anisotropy of the SiCf/SiC material, the obtained surface characteristics are closely dependent on the laser scanning direction to the SiC fibers, resulting in different groove morphology. The element composition and phase analysis of the machined surface indicate that the main deposited product is SiO2 and the carbon substance. The results can provide preliminary technical support for controlling the machining quality of ceramic matrix composites.

Weak Coordinating Character of Organosulfonates in Oriented Silica Films: An Efficient Approach for Immobilizing Cationic Metal-Transition Complexes.

Iron (II) tris(2,2′-bipyridine) complexes, [Fe(bpy)3]2+, have been synthesized and immobilized in organosulfonate-functionalized nanostructured silica thin films taking advantage of the stabilization of [Fe(H2O)6]2+ species by hydrogen bonds to the anionic sulfonate moieties grafted to the silica nanopores. In a first step, thiol-based silica films have been electrochemically generated on indium tin oxide (ITO) substrates by co-condensation of 3-mercaptopropyltrimethoxysilane (MPTMS) and tetraethoxysilane (TEOS). Secondly, the thiol function has been modified to sulfonate by chemical oxidation using hydrogen peroxide in acidic medium as an oxidizing agent. The immobilization of [Fe(bpy)3]2+ complexes has been performed in situ in two consecutive steps: (i) impregnation of the sulfonate functionalized silica films in an aqueous solution of iron (II) sulfate heptahydrate; (ii) dipping of the iron-containing mesostructures in a solution of bipyridine ligands in acetonitrile. The in situ formation of the [Fe(bpy)3]2+ complex is evidenced by its characteristic optical absorption spectrum, and elemental composition analysis using X-ray photoelectron spectroscopy. The measured optical and electrochemical properties of immobilized [Fe(bpy)3]2+ complexes are not altered by confinement in the nanostructured silica thin film.

Thermal Degradation and Organic Chlorine Removal from Mixed Plastic Wastes

Plastic waste accumulation has been growing due to the increase in plastic generation and the lack of infrastructure for recycling. One of the approaches is to treat the mixed plastic waste (MPW) through thermal processes to produce feedstocks for other applications. However, the presence of polyvinyl chloride (PVC) in MPW would produce HCl during processing and has negative impacts (emission, catalyst poisoning, etc.). In addition, due to the high heterogeneity of MPW, it is difficult to generate consistent experimental data. In this study, MPW was homogenized through double compounding–extrusion and then formed into a sheet to be treated at 400 °C. The solid products at various mass losses were characterized by heat and chlorine content, Fourier-transform infrared (FTIR) spectroscopy, and elemental composition analysis. It was found that the thermal degradation of MPW started at ~260 °C. The chlorine removal efficiency increased with mass loss and reached an asymptotic value of ~84% at ~28% mass loss, and the remaining chlorine can be attributed to inorganic sources. A PVC de-chlorination model was developed for MPW using TGA data for PVC and MPW to determine organic chlorine removal efficiency. These results show that PVC de-chlorination was not affected by other plastics at this temperature. As the mass loss increases, the heat content first increases and then decreases. It was found that mass loss is a universal parameter for organic chlorine removal efficiency and heat content. The elemental composition analysis and FTIR spectroscopy also shed more light into the chemical changes during MPW thermal degradation.

Improved ANN-Based Approach Using Relative Impact for the Prediction of Thermal Coal Elemental Composition Using Proximate Analysis.

The basic properties of coal influence various procedures of power generation, such as the design of power generation plants, estimation of the current condition of boilers, and total efficiency of power plants. The elemental composition is a needed factor in evaluating the process of chemical conversion and predicting the flow of flue gas and the quality of air in coal combustion. In the past, several relationships have been established using ultimate and proximate analyses. This study aims to predict the elemental compositions of 104 thermal coals used for coal-fired power plants in South Korea using an artificial neural network (ANN) that uses proximate analysis values as input parameters. The ANN-based model was optimized with six activation functions and four hidden layers after evaluating various performance indices, including R2, mean square error (MSE), and epoch, then additional calculations were derived to compare performances from previous research using the mean absolute error (MAE), average absolute error, and average bias error. It was found that the best topology was established using the Levenberg–Marquardt activation function and 10 hidden layers, resulting in the highest R2 value and smallest MSE of all topologies tested. As a result, the relative impact on calculation accuracy was derived from ANN hidden layers to analyze prediction accuracies of carbon, hydrogen, and oxygen compositions. Accuracy was improved over previous results by 4.71–0.91% via coal rank division topology optimization. Based on the MAE, the current results are even close in performance to those of adaptive neuro-fuzzy inference systems. They also outperformed previous research models by 5.40 and 7.39% in terms of MAE accuracy. Applicability of the ANN was also analyzed with limitations of the chemical composition of ANNs and present reinforcement measures in the future studies through qualitative analysis comparisons based on Fourier transform infrared spectroscopy. Consequently, the relative effect was derived from the ANN hidden layer weight for specific calculation of the relationship between elemental composition and proximate analysis properties. As a result, it was possible to qualitatively analyze how the proximate analysis value affects the composition of elements and calculate the ratio accordingly. The findings of this study provide an improved and efficient approach to predicting the elemental composition of thermal coal, based on data from South Korean power plants. Also, further research can follow schematics from this study with the applicability and accessibility of the ANN.

Development of 2nd Generation Thin Film Photovoltaics Based on CZTS Absorber Layer and ZnS Window Layer

Among the second-generation solar cells, thin-film solar cells based on CIGS, CZTS and CdTe are well known due to their higher efficiencies, low cost and simple fabrication techniques. In this proposed work, we are committed to developing CZTS and ZnS thin films for second-generation thin-film photovoltaics. CZTS and ZnS have energy band gap of 1.4-1.5 eV and 3.6 eV, while their light absorption coefficients are 104 cm-1 and 3.3×104 cm-1 respectively. In thin film solar cells, absorber layer consists of photovoltaic material that should have optimal bandgap close to 1.34 eV. Moreover, a wide band gap window layer acts as p-n junction with absorber layer. In this work, we are reporting the synthesis of CZTS and ZnS thin films via wet chemistry route using spin coating method. Deposition of thin films on SLG substrate were carried out at specific process parameters such as spinning speed, concentration of precursors and annealing temperature to get the optimized thin film suitable for photovoltaic applications. Surface morphology and elemental compositional analysis investigated through SEM and EDX spectroscopy respectively. Electrical and optical properties were examined via Hall effect measurements and UV-VIS NIR spectrophotometry respectively. In addition micro-chemical and functional group analysis were conducted by FRIT spectroscopy. Keywords: Thin film PV, wet-chemistry, CZTS, ZnS

VO2 thin film based highly responsive and fast VIS/IR photodetector

The VO2 (M1) thin film has attracted significant attention due to its abrupt semiconductor to metal transition (SMT) near room temperature and diverse optoelectronic applications. In this work, pure VO2 (M1) phase thin film has been grown on the silicon substrate using a pulsed laser deposition technique. The Raman spectroscopy results confirmed the deposition of pure VO2 (M1) phase thin film. The X-ray photoelectron spectroscopy (XPS) showed that the deposited vanadium oxide thin film is mainly composed of VO2. The field emission scanning electron microscopy (FESEM) showed a smooth, continuous, and well-covered surface morphology. The elemental composition analysis of the deposited thin film using energy-dispersive X-ray spectroscopy (EDX) exhibited the presence of V and O in the deposited thin film. The VO2 (M1) thin-film device with a simple planar structure displayed resistance change of more than two orders of magnitude with increasing and decreasing temperature displaying a sharp semiconductor to metal transition (SMT) behavior with a transition width of ∼10 °C and transition temperature of ∼67 °C; a property associated with VO2 (M1). The photo-detection results of the VO2 (M1) based device revealed a better response upon illumination with 650 nm light at 0.15 mW/cm2 compared to 980 nm light at 0.34 mW/cm2. The rise time (tr) and fall time (tf) of ∼1.57 and ∼1.64 ms were achieved upon illumination with 650 nm light at 0.15 mW/cm2 while ∼1.67 and ∼4.12 ms upon illumination with 980 nm light at 0.34 mW/cm2. The photo-responsivity has been measured as ∼353 mA/W and ∼78 mA/W for 650 nm and 980 nm light, respectively. The response time and responsivity of the phase pure VO2 (M1) thin film for the Visible and IR light has been significantly improved compared to the earlier reported vanadium dioxide thin films based photodetectors.

Surface modification of copper selenide for reliable non-enzymatic glucose sensing

Improvement in the catalytic activity of the electrode material can be achieved by altering surface morphology. Herein, the effect of complexing agent (ammonia, NH4OH) concentration on the surface morphology of copper selenide (Cu3Se2) film electrodes synthesized using the chemical bath deposition method was evaluated. Thin films of Cu3Se2 were characterized using structural, morphological, and elemental composition analyses. The electrochemical glucose sensing performance of films was evaluated using cyclic voltammetry and i-t amperometry techniques. The broad linear range of detection (2.8 μM–1.5 mM of glucose concentration) and high sensitivity (18,500 μA/mM cm2) as well as the low limit of detection limit (2.8 μM) project Cu3Se2 films with spherical nanoparticles morphology as a promising electrode material for non-enzymatic glucose detection application. The measurement of glucose levels from a human blood sample using Cu3Se2 films confirms practical applicability for further device fabrication.

Luna – 25 robotic arm: Results of experiment with analog of lunar regolith in lunar like conditions

The lunar lander developed by Russia for the first near polar mission Luna – 25 is equipped with a compact and multifunctional robotic arm (Lunar Manipulator Complex, LMC) designed for contact operations with the lunar regolith. The robotic arm shall excavate the lunar regolith down to tens of centimeters, collect regolith samples and deliver them to a laser ionization mass spectrometer for the elemental and isotopic composition analysis. Luna – 25 enters the final preparation stage to be ready for the launch in 2022. As a part of this activity special robotic arm ground tests were successfully conducted at Earth facilities imitating lunar like conditions. It was tested how the robotic arm could excavate the analog of lunar regolith mixed with different concentrations of water and frozen to the cryogenic temperatures (−100 °C). It was shown that mechanical strength of the frozen analog of the lunar regolith significantly increases with the increase of water ice concentration and demonstrated that the robotic arm is capable of excavating trenches and collecting samples in the ice rich analog of the lunar regolith homogeneously mixed with 1.5 wt % of water ice.

Effect of Saccharides Coating on Antibacterial Potential and Drug Loading and Releasing Capability of Plasma Treated Polylactic Acid Films.

More than half of the hospital-associated infections worldwide are related to the adhesion of bacteria cells to biomedical devices and implants. To prevent these infections, it is crucial to modify biomaterial surfaces to develop the antibacterial property. In this study, chitosan (CS) and chondroitin sulfate (ChS) were chosen as antibacterial coating materials on polylactic acid (PLA) surfaces. Plasma-treated PLA surfaces were coated with CS either direct coating method or the carbodiimide coupling method. As a next step for the combined saccharide coating, CS grafted samples were immersed in ChS solution, which resulted in the polyelectrolyte complex (PEC) formation. Also in this experiment, to test the drug loading and releasing efficiency of the thin film coatings, CS grafted samples were immersed into lomefloxacin-containing ChS solution. The successful modifications were confirmed by elemental composition analysis (XPS), surface topography images (SEM), and hydrophilicity change (contact angle measurements). The carbodiimide coupling resulted in higher CS grafting on the PLA surface. The coatings with the PEC formation between CS-ChS showed improved activity against the bacteria strains than the separate coatings. Moreover, these interactions increased the lomefloxacin amount adhered to the film coatings and extended the drug release profile. Finally, the zone of inhibition test confirmed that the CS-ChS coating showed a contact killing mechanism while drug-loaded films have a dual killing mechanism, which includes contact, and release killing.

Clay and soil organic matter drive wood multi-elemental composition of a tropical tree species: Implications for timber tracing

Forensic methods to independently trace timber origin are essential to combat illegal timber trade. Tracing product origin by analysing their multi-element composition has been successfully applied in several commodities, but its potential for timber is not yet known. To evaluate this potential the drivers of wood multi-elemental composition need to be studied. Here we report on the first study relating wood multi-elemental composition of forest trees to soil chemical and physical properties.We studied the reactive soil element pools and the multi-elemental composition in sapwood and heartwood for 37 Azobé (Lophira alata) trees at two forest sites in Cameroon. A total of 46 elements were measured using ICP-MS. We also measured three potential drivers of soil and wood elemental composition: clay content, soil organic matter and pH. We tested associations between soil and wood using multiple regressions and multivariate analyses (Mantel test, db-RDA). Finally, we performed a Random Forest analysis of heartwood elemental composition to check site assignment accuracy.We found elemental compositions of soil, sapwood and heartwood to be significantly associated. Soil clay content and organic matter positively influenced individual element concentrations (for 13 and 9 elements out of 46 respectively) as well as the multi-elemental composition in wood. However, associations between wood and topsoil elemental concentrations were only significant for one element. We found close associations between element concentrations and composition in sapwood and heartwood. Lastly, the Random Forest assignment success was 97.3 %.Our findings indicate that wood elemental composition is associated with that in the topsoil and its variation is related to soil clay and organic matter content. These associations suggests that the multi-elemental composition of wood can yield chemical fingerprints obtained from sites that differ in soil properties. This finding in addition to the high assignment accuracy shows potential of multi-element analysis for tracing wood origin.

Microstructure, guiding performance and micro-spectroscopy characterization of Ce:LuAG crystal induced by direct femtosecond laser writing

Dual-line waveguides in Ce:LuAG crystal are fabricated by femtosecond laser using 1030 nm, 450 fs pulses at a 100 kHz repetition rate. The microstructure and composition of femtosecond-laser induced waveguides are studied in detail using SEM, TEM and EDX elemental composition analyses. Efficient single-mode guidance is obtained in the type II waveguide structures with relatively low propagation loss along both TE and TM polarization at 632.8 nm. Based on confocal micro-Raman spectroscopy, the strain-affected regions and the lattice-damaged tracks are demonstrated. The contribution of each effect to the refractive-index distribution are quantitatively determined in combination with beam propagation calculations. The generation of yellow-green fluorescence emission is demonstrated under excitation at 405-nm, retaining well luminescent performance in the Ce:LuAG waveguide.

Indoor-outdoor relationship of submicron particulate matter in mechanically ventilated building: Chemical composition, sources and infiltration factor

To evaluate the impact of outdoor particulate pollution on indoor air quality, the chemical composition and sources of submicron aerosol particles (PM1) were studied indoors and outdoors. Measurements were carried out during the heating season from October 15, 2020, to February 8, 2021, at the Center for Physical Sciences and Technologies in Vilnius, Lithuania. Online measurements of PM1 chemical composition were performed using an Aerosol Chemical Speciation Monitor (ACSM (organics, sulfate, and nitrate)) and an Aethalometer (equivalent black carbon, BC). In parallel with the online measurements, filter-based elemental composition and 14C analysis of PM1 were performed using a Particle-Induced broad-beam X-ray Emission (PIXE) and a Single Stage Accelerated Mass Spectrometer (SSAMS), respectively. The source apportionment results showed a dominant contribution of biomass burning to the total carbonaceous aerosol particles, including primary (30%) and secondary (40%) fractions. According to the enrichment factors, the main source of trace elements was road dust resuspension (30%), while anthropogenic emissions accounted for only 13% of trace elements. The infiltration factor (Finf) of all studied PM1 constituents was low (Finf∼0.03). This result indicates that the three-stage building filter system (G4-F7-F9) provides high protection against particle pollution of different origins and significantly reduces indoor exposure to PM1. The changed chemical composition of indoor PM1 can be attributed to species-specific evaporation and some minor indoor sources.

Biochar Particles Obtained from Agricultural Carob Waste as a Suitable Filler for Sustainable Biocomposite Formulations.

In the context of sustainable and circular economy, the recovery of biowaste for sustainable biocomposites formulation is a challenging issue. The aim of this work is to give a new life to agricultural carob waste after glucose extraction carried out by a local factory for carob candy production. A pyrolysis process was carried out on bio-waste to produce biofuel and, later, the solid residual fraction of pyrolysis process was used as interesting filler for biocomposites production. In this work, biochar particles (BC) as a pyrolysis product, after fuels recovery of organic biowaste, specifically, pyrolyzed carobs after glucose extraction, were added on poly(butylene-adipate-co-terephthalate), (PBAT), at two different concentrations, i.e., 10 and 20 wt%. The BC have been produced using three pyrolysis processing temperatures (i.e., 280, 340 and 400 °C) to optimize the compositions of produced solid fractions and biofuels. The resulting particles from the pyrolysis process (BC280, BC340 and BC400) were considered as suitable fillers for PBAT. Firstly, the BC particles properties were characterized by elemental composition and spectroscopy analysis, particle size measurements and evaluation of radical scavenging activity and efficiency. Moreover, PBAT/BC composites were subjected to analysis of their rheological and thermal behavior, morphologies and mechanical properties. In addition, accelerated weathering, monitored by both tensile test and spectroscopic analysis, was carried out, and obtained results show that the biochar particles can exert a beneficial effect on photo-oxidation delay of PBAT matrix.

Trace and Rare Earth Element Partitioning in Organic Fractions of Mudstones during the Oil Formation

In order to investigate trace and rare earth element partitioning in organic fractions of mudstones, this study isolated organic fractions of mudstones, including insoluble organic fraction (kerogen), soluble organic fraction (extract), or expelled hydrocarbon (reservoir solid bitumen), and the isolated organic fractions and their corresponding whole rocks for trace and rare earth element compositions were measured. Analysis of trace and rare earth element compositions in organic fractions of lacustrine and marine mudstones revealed that mudstone kerogens were more enriched in rare earth elements (REE) and redox-sensitive trace elements (e.g., U, Mo, and Ni) relative to corresponding whole rocks. During the oil generation, middle rare earth elements (Sm-Ho), especially Eu, migrated from kerogen to extract more easily than the rest REE. The Eu was easily transferred to soluble hydrocarbon under the acidic and reducing environments formed by oil generation, resulting in the higher concentrations of Eu relative to its neighboring REE (Sm and Gd) and the pronounced positive Eu anomalies. Transition metal elements (e.g., Mo, V, Cr, Co, Ni, Cu, and Zn) also more easily released from kerogen than the rest elements, especially V and Ni. The enrichment and mobilization of trace elements in organic fractions of mudstones, such as Mo, U, V, Ni, and Ba, are closely related with their geochemical behaviors during the depositional and early digenetic processes, providing the potential information for predicting the distribution characteristics of trace elements in the expelled hydrocarbons of mudstones (e.g., crude oil and solid bitumen) and fingerprinting of oil to source.

Recent and ancient evolutionary events shaped plant elemental composition of edaphic endemics: a phylogeny-wide analysis of Iberian gypsum plants.

Summary The analysis of plant elemental composition and the underlying factors affecting its variation are a current hot topic in ecology. Ecological adaptation to atypical soils may shift plant elemental composition. However, no previous studies have evaluated its relevance against other factors such as phylogeny, climate or individual soil conditions.We evaluated the effect of the phylogeny, environment (climate, soil), and affinity to gypsum soils on the elemental composition of 83 taxa typical of Iberian gypsum ecosystems. We used a new statistical procedure (multiple phylogenetic variance decomposition, MPVD) to decompose total explained variance by different factors across all nodes in the phylogenetic tree of target species (covering 120 million years of Angiosperm evolution).Our results highlight the relevance of phylogeny on the elemental composition of plants both at early (with the development of key preadaptive traits) and recent divergence times (diversification of the Iberian gypsum flora concurrent with Iberian gypsum deposit accumulation). Despite the predominant phylogenetic effect, plant adaptation to gypsum soils had a strong impact on the elemental composition of plants, particularly on sulphur concentrations, while climate and soil effects were smaller.Accordingly, we detected a convergent evolution of gypsum specialists from different lineages on increased sulphur and magnesium foliar concentrations.

Electrochemical recovery of phosphate from synthetic wastewater with enhanced salinity

Electrochemical recovery of phosphorus from synthetic wastewater using a sacrificial Mg anode has been explored as a function of key parameters, including pH, voltage, and salinity. The effect of chloride (NaCl) concentrations in the range of 0–1500 mM on both Mg corrosion and phosphate precipitation was investigated in acidic and alkaline (i.e., pH 4 and 8) solutions of dihydrogen ammonium phosphate. The primary phosphate precipitate was expected to be struvite (MgNH4PO4·6H2O), and collected precipitates were characterized to determine composition and phase. Batch experiments were run at selected potentials identified by linear sweep voltammetry experiments. Higher corrosion current densities (jcorr), which indicated higher Mg dissolution and corrosion rates (υcorr), were achieved in solutions with higher pH and salt concentrations. Both Mg corrosion and phosphate recovery were proportional to [Cl−], so 1500 mM Cl− at pH 8 resulted in increased Mg dissolution and phosphate recovery by ∼5x and 2x, respectively, compared to the solution without chloride. Elemental composition analysis (ion chromatography), crystallography (X-ray diffraction), surface chemical composition analysis (Fourier-transform infrared spectrometry) and characterization (scanning electron microscopy images) of precipitates suggested the presence of struvite. The Mg/P composition of precipitates formed in 1000 mM Cl− solution showed a greater extent of deviation from the theoretical molar ratio in struvite when the electrochemical cell was operated at more positive anodic overpotential and low initial solution pH. The elevated Mg/P ratio could indicate the presence of mixed precipitates. Simulation of product distribution analysis and specific energy requirement results suggest optimum electrochemical struvite production in the pH range of 8–10 in the presence of chloride.

Quantification Model of Residual Biomass in Citrus Uprooting

In this paper, the aerial biomass of citrus plantations in Spain was evaluated using destructive methods. Before cutting down the trees, their geometric variables were measured: trunk diameter at 10 cm from the ground (Dt), trunk perimeter at 10 cm from the ground (Pm), mean crown diameter (Dc), canopy height (Hc), and maximum crown height (Hmax). After geometric characterization of the tree, it was felled. This was performed with a chainsaw about 10 cm above the ground. After cutting down, trees with and without leaves were weighed, and biomass variables such as moisture, calorific value, elemental composition, and proximate analysis were measured. The predictive models obtained showed an r2 of 0.78. According to our analysis, in plantations in Spain, where the average plantation pattern is 4 × 4 m, the amount of carbon stored in a plot is 15 t of C per hectare. If leaves and wood are counted, the energy density in citrus plots can be estimated at 900 MJ/tree. However, if only wood is included in the calculation, the accumulated energy per tree is 750.3 MJ/tree, which represents 5.6 × 105 MJ/ha.

Polychromy in Roman Portraits from Asido (Medina Sidonia, Cádiz, Spain). Livia, Germanicus and Drusus Minor

This paper presents a recent study on a Roman period marble sculpture depicting Empress Livia and the portraits of Germanicus and Drusus Minor, found at the praesidium of Asido (Medina Sidonia, Cádiz, Spain). The sculptures retain extensive evidence of their original polychromy. The properties and spatial distribution of these pigment remains were investigated by portable non-invasive and micro-destructive techniques, applying digital microscopy, and UV/VIS/NIR/SWIR spectroscopy, portable XRF and SEM–EDS analysis. The study revealed the presence of Egyptian blue and ochre on Livia’s mantle and charcoal black on Livia’s eyes and hair, remains that were not clearly visible to the naked eye. This is a significant approach, used to identify colours on ancient marble sculpture, which transforms our understanding of these unique pieces. Elemental composition analysis by pXRF has confirmed the evidence of pigments, furthermore supported by the Raman results, making it possible to develop and reconstruct the colour palette that originally brought these sculptures to life in vibrant polychrome. The research offers a new methodology for identifying pigments on marble sculpture and opens new ways for investigating other types of material culture aided by the development of the analytical equipment mentioned.

Sandwich-Structured h-BN/PVDF/h-BN Film With High Dielectric Strength and Energy Storage Density.

Energy storage film is one of the most important energy storage materials, while the performance of commercial energy storage films currently cannot meet the growing industrial requirements. Hence, this work presents a h-BN/PVDF/h-BN sandwich composite structure film prepared by laminating a large area of ultrathin hexagonal boron nitride (h-BN) and polyvinylidene fluoride (PVDF), the existence of which was confirmed by using an optical microscope and elemental composition analysis based on scanning electron microscopy and X-ray diffraction. This film has an ultrahigh dielectric strength of 464.7 kV/mm and a discharged energy density of up to 19.256 J/cm3, which is much larger than the commercial energy storage film biaxially oriented polypropylene (BOPP) (<2.5 J/cm3). Although the thickness of the h-BN film is only 70 nm compared with that of PVDF (about 12 μm), the dielectric strength of the sandwich-structured film presents a great increase. It is because of the excellent insulation performance of the h-BN film that helps to resist the electron injection and migration under high electric field, and then suppress the formation and growth of the breakdown path, leading to an improvement of the charge–discharge efficiency.

An ionic covalent organic framework loaded with terbium-based probe for the sensing and removal of chrysolepic acid: Characterization and ratiometric behavior

Chrysolepic acid (CA) is a widely-used chemical product and considered hazardous for ecosystem and human health, which makes its removal as important as its sensing. In this work, a composite structure (denoted as Tb–COF, with a structural composition of C 162 H 120 N 18 O 12 Br 3 ·C 21 H 9 N 3 O 12 Tb 1 ) was synthesized, consisting of an ionic covalent organic framework (denoted as I–COF, with a structural composition of C 162 H 120 N 18 O 12 Br 6 ) and a terbium-based dopant/emitter (denoted as Tb(DPA) 3 3− , DPA = pyridine-2,6-dicarboxylic acid). Tb–COF was identified by means of single crystal analysis, infrared (IR) spectra, X-ray diffraction (XRD), porosity analysis, SEM (scanning electron microscope)/TEM (transmission electron microscope) and elemental composition analysis. The dopant loading level in Tb–COF was determined as 41%. Both green emission from Tb-based dopant and red emission from I–COF host were observed. The presence of CA quenched I–COF emission but enhanced dopant emission, resulting in ratiometric sensing signal. A linear calibration curve was demonstrated, with fitting equation of I/I 0 = 1.223 + 6.709 × 10 5 M −1 [CA], R 2 = 0.996, within [CA] region of 0–9 μM. The key sensing/adsorption process was revealed as the adsorption of I–COF micropores for CA molecules, which endowed Tb–COF with a good selectivity over competing species. I–COF adsorption/removal feature for CA was tentatively evaluated. • An ionic covalent organic framework was synthesized and modified with luminescent ionic Tb(III) emitter. • The as-synthesized Tb–COF showed weak Tb(III) emission and strong red COF emission. • After adding CA, Tb(III) emission was increased with COF emission weakened greatly, showing sensing behavior. • The adsorption and removal performance of Tb–COF was investigated as well.