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• High level of PFOA was found in fluoropolymer raw materials and products made in China. • The concentration of PFOA in fluoropolymer raw materials was higher than products. • Hexafluoropropylene oxide oligomers have been heavily used to substitute PFOA in fluoropolymer manufacture in China. • HFPO-TrA, a PFOA substitute, was found in high level in some emulsion samples. Perfluorooctanoic acid (PFOA), its salts, and related compounds were listed as new persistent organic pollutants by the Stockholm Convention in 2019. In this study, the occurrence of residues of PFOA and other per- and polyfluoroalkyl substances (PFASs) in raw materials and fluoropolymer products from the Chinese fluoropolymer industries are reported for the first time. The PFOA concentrations in raw materials and fluoropolymer products were in the range of 6.7 to 1.1 × 106 ng/g, and

The packing of rod-like particles has arisen in a variety of scientific and industrial applications. For the factors that attribute to the packing properties of such particles, elongation effect is one of the most important. However, rod-like particles can be easily assembled into non-convex shapes, in which the effects of non-convex deformations should be concerned. In this paper, the dense random packings of identical intersecting spherocylinders with central symmetry are numerically simulated through an analytical model and the relaxation algorithm. The maximally dense random packing (MDRP) states of 2D and 3D intersecting spherocylinders with various aspect ratios are determined from the order maps. In the MDRP states, the specific volume V , defined as the reciprocal of the packing density ϕ , shows a highly linear correlation with the aspect ratio ( w ≥ 1.0), which is similar to the monophasic packing of spherocylinders. This indicates that the elongation effect is the main shape factor that attributes to the packing density. Consequently, the explicit formulas to predict the packing densities of 2D and 3D intersecting spherocylinders are built as single-variable functions of the aspect ratio. The dense random packing density of 2D intersecting spherocylinders equals to that of identical spherocylinders when w = 1.25. This suggests that a balance exists between the relative excluded volume effect and the multi-point contact effect to the packing density of non-convex particles. [ABSTRACT FROM AUTHOR]

A spherocylinder, a convex 3D object consisting of a cylinder with two hemispherical ends, can possess a wide range of aspect ratios and is one of the most studied non-spherical particle shapes. Previous investigations on disordered spherocylinder packings yielded inconsistent packing characteristics, especially the packing density φ, indicating that density alone is not sufficient to uniquely characterize a packing. In this paper, we delineate in the density–order–metric diagram (i.e. order map) the border curve that separates geometrically feasible and infeasible packings of congruent spherocylinders via the geometric-structure approach, i.e., by generating and analyzing a large number of packing configurations with a diversity of densities and degrees of order generated via a relaxation algorithm. We find that the border curve possesses a sharp transition as the packing density increases, i.e., the initial increase of φ is not associated with any notable increase of the degree of order, while beyond a threshold φ value, the increase of density is strongly positively correlated with the increase of order. This allows us to propose the concept of maximally dense random packing (MDRP) state for spherocylinders, which corresponds to the transition point in the boarder curve and characterizes the on-set of nontrivial spatial correlations among the particles. It can also be considered as the maximally dense packing arrangement of spherocylinders without nontrivial spatial correlations. The degree of order of a spherocylinder packing is quantified via the nematic order parameter ( S ) and the local order metric ( S Local ), which respectively characterize the level of global orientational order and local order in particle clusters. The latter metric S Local , which measures the average order in the neighborhoods of particles with the second Legendre polynomial, is a new order metric for spherocylinder systems. We find that the packing density of the MDRPs initially increases with the increase of the aspect ratio w from 0, and reaches the maximal value of 0.725 when w = 0.5, then drops with further increase of w . The MDRP at w = 0.5 is verified to be jammed via a Monte Carlo jamming-testing algorithm and thus, should also represent the maximally random jammed (MRJ) packing state as well. [ABSTRACT FROM AUTHOR]

• Eight-carbon PFAS were dominant in the Bohai Sea. • The highest ∑PFAS were observed in the Laizhou Bay for seawater and in the Liaodong Bay for sea sediments, respectively. • Six primary sources were revealed by using PMF 5.0 software. • The environmental risk of PFAS was not high in the Bohai Sea. In this study, the occurrence, distribution, sources, and risk of 29 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in four kinds of environmental matrices in the Bohai Sea were investigated. The ∑PFAS concentrations were in the range of 0.40 ~ 61.4 ng/g dry weight (dw) in inflow river sediments, 0.48 ~ 61.4 ng/g dw in soil near river inflow, 0.37 ~ 4.18 ng/g dw in sea sediments, and 13.3 ~ 718 ng/L in seawater. PFAS with eight carbons accounted for > 62.2% by mass, in all samples. Perfluorooctanoic acid (PFOA) was the dominant PFAS both by mass and occurrence. Seawater from Laizhou Bay (south of the Bohai Sea) and sediments of Liaodong Bay (northeast of the Bohai Sea) had the highest levels of ∑PFAS. The sediment–water partition coefficient and organic carbon content normalized partition coefficient (log K d and log K oc ) were calculated using measured PFAS concentrations to determine their distribution in seawater and sea sediments. The values of log K d and log K oc values increased with the increasing CF 2 units for perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs). Six primary sources were identified in this region, including aqueous film-forming foams (AFFF), metal plating, food packages, fluorine chemical industry, fluoropolymer manufacture, and domestic pollution. The risk quotient (RQ) values of PFAS were all < 1, indicating that organisms of the Bohai Sea were at low risk of PFAS exposure. [ABSTRACT FROM AUTHOR]

Realizing multiple stimuli responsiveness in organic molecular systems is very important and highly desirable to broaden their potential applications in smart materials. Such stimuli responsive materials are usually required in nontrivial multistep synthesis. In the present research, a series of asymmetrical naphthalene diimide derivatives (NDIs), which display interesting multiple external stimuli responsiveness including ultrafast photochromism and chemical stimulation chromism, with the generations of organic radical anions and charge transfer, were obtained by simple synthetic process. Importantly, the multicolored functionality was ingeniously achieved by mixing commercially available materials (guest molecules) and the readily-made asymmetrical NDIs through mechanical grinding under solvent-free conditions. Noteworthy the charge transfer processes, strongly depending on the distinctive structures of NDIs molecules as well as the weak intermolecular interactions, can be induced by external stimuli (i. e. light, chemical, or grinding). Subsequently, significant stimuli responsiveness as well as multicolored properties were realized and the underlying weak interactions-assisted charge transfer mechanism was thoroughly unearthed. A series of asymmetrical naphthalene diimide derivatives (NDIs) display interesting multiple external stimuli responsiveness including ultrafast photochromism and chemical stimulation chromism, which result from the generations of organic radical anions and charge transfer. Moreover, this system shows mechanical grinding toning with certain organic molecules, which have potential applications in smart materials. [Display omitted] • Radical-doped asymmetrical NDIs possess significant photochromism, chemical stimuli chromism and mechanical grinding toning. • Weak interactions-assisted charge transfer enable the generation of organic radicals, leading to multiple stimuli chromism. • Involved solvent-free synthesis and charge transfer process play key role in green synthesis and electron transfer chemistry. [ABSTRACT FROM AUTHOR]

Both legacy and emerging per- and polyfluoroalkyl substances (PFAS) have been found to be threats to human health. In particular, fetuses are sensitive to xenobiotics and the placenta functions as a significant barrier for environmental pollutants. The placental transfer of PFAS is closely related to their interactions with proteins. In this study, 54 human placental samples were collected to investigate the occurrence of legacy and emerging PFAS in human placenta, including perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs), and fluorotelomer sulfonates (FTSAs). Among the legacy PFAS, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) were detected in all samples, with PFOS and PFOA being the two predominant (mean: 0.457 and 0.242 ng/g wet weight, respectively). Among the emerging PFAS, 6:2 Cl-PFESA was detected in all samples with the mean value of 0.104 ng/g wet weight, while the detect frequency (DF) of 8:2 Cl-PFESAs was only 24%. The concentration and DF of the four FTSA congeners were low in the placentas. Molecular docking calculation results showed that the binding affinities of PFAS to the human serum albumin (HSA) were increased with chain length in each category except for the PFCAs, of which the perfluoroundecanoic acid (PFUnDA) was the turning point of binding affinity to HSA. For PFSAs, their binding affinities to organic anion transporter 4 (OAT4) were increased with the chain length except for the sodium perfluoro-1-heptanesulfonate (PFHpS) and sodium perfluoro-1-nonanesulfonate (PFNS). The calculation results demonstrated that the placental transfer of PFAS is closely related to chain length. The findings in the study can help better understand the occurrence of the PFAS in the human placenta and the placental transfer mechanisms of PFAS in human beings. Image 1 • The concentration and DF of 8:2 Cl-PFESA and FTSAs were low, while 6:2 Cl-PFESA was detected widely in human placentas. • In the human placentas, the main congeners of PFAS were still legacy PFAS. • The binding abilities of PFAS to HSA increased with chain length except for PFCAs, of which PFUnDA was the turning point. • The binding abilities of PFASs to OAT4 increased with the chain length of PFAS except for PFHpS and PFNS. • The placental transfer of PFAS is closely related to their chain length. The main congeners of PFAS in human placentas were legacy PFAS. The binding affinities of PFAS to HSA and OAT4 were closely related to the chain length. [ABSTRACT FROM AUTHOR]

Screening ideal partner materials for the CsPbI 3 perovskite is crucial for developing all-inorganic perovskite-based tandem solar cells. Here, we quantize the performance of all-inorganic tandem solar cells combining the CsPbI 3 perovskite with c-Si, GaAs, CdTe, CIGS, and CsSnI 3 , by analyzing the measured spectral efficiencies and developing macroscopic continuum device (MCD) model. Firstly, we integrate the MCD model and the principles of detailed balance (Shockley-Queisser limit model, SQM) to investigate the top CsPbI 3 solar cell with varying thickness and the rear sub-cell with different bandgaps. Without considering the nonradiative recombination and absorptivity in the rear sub-cell, an efficiency of over 32% can be reached by selecting the low bandgap materials (E gap ~ 1.1 eV) as the rear sub-cell. Furthermore, after the simulation by MCD model that takes the charge recombination, absorptivity and optimal thicknesses for both sub-cells in tandem architectures into account, CIGS is found to be one of the best junction partners for CsPbI 3. During the simulations, a unique bisection search algorithm is used to guarantee that the continuity of electric potential near the junction layer and the current matching of sub-cells in the tandem solar cells. As a result, a CsPbI 3 (470 nm)/CIGS(2000 nm) tandem solar cell with the best-modeled efficiency of 24.40% can be achieved, which is affirmed by a recent experimental result. Finally, we simulate the corresponding bifacial tandem photovoltaic device, and the optimal modeled efficiency can be further enhanced to 25.58%. Image 1 • Tandem solar cells combining CsPbI3 with c-Si, GaAs, CdTe, CIGS, and CsSnI3 are theoretically analyzed with two models. • A bisection search algorithm is used to guarantee the continuity of electric potential and the current matching. • Hybrid MCD/SQM and complete MCD models are used to screen the parameters and simulate the photovoltaic performances. • An efficiency of >32% can be achieved by using the materials with E g around 1.1 eV as the rear cell with the MCD/SQM model. • With MCD simulations, the CsPbI 3 (470 nm)/ CIGS(2000 nm) tandem solar cell demonstrates the best-modeled efficiency of 24.40%. [ABSTRACT FROM AUTHOR]

Experiments and peridynamic simulations of the split-Hopkinson pressure bar (SHPB) have been conducted to investigate the dynamic mechanical behaviors of magnesium aluminate (Mg-Al) spinel. The high-speed camera and scanning electron microscopy were used to observe the failure process and the fracture surface. In our modified model, the crystal orientation and grain boundary strength were explicitly quantified, accompanied by the dual-horizon peridynamic technique, resulting in high calculation accuracy and efficiency. Then effects of the stress state and strain rate on the failure mechanism of spinel have been investigated with the damage evolution process. Micro-pores tend to be generated at the intersection of grain boundaries, while cracks will propagate along these micro-pores, leading to trans-granular and inter-granular failures. Finally, the microstructure effects on the mechanical properties of spinel have been systemically investigated. The strength and distribution of grain boundaries were found to significantly affect the strength and crack propagation of Mg-Al spinel. [ABSTRACT FROM AUTHOR]

A polyethylenimine (PEI)-scaffolded and functionalized graphene aerogel, PEI-GO-AG, was prepared and utilized as a highly selective adsorbent for the extraction of thorium (Th) (IV) from three lanthanides (Ln) (III) elements. The three dimensional (3D)-porous structure of the adsorbent was established by the cross-linking effect of PEI via a one-step hydrothermal strategy and preserved by a freeze-drying treatment to avoid the collapse of the structure. The extractive efficiency of PEI-GO-AG displayed a sensitive dependence on the beginning mass ratio of PEI/graphene oxide (GO) in the hydrothermal step because of its significant influence on the hydrophilicity and the amounts of introduced binding sites of the adsorbent.. Besides, a density function theory (DFT)-based theoretical calculation was performed, confirming the higher stability of Th (IV)-PEI-GO-AG than that of Ln (III)-PEI-GO-AG. Ascribed to these contributions, the as-prepared adsorbent showed high selectivity towards Th (IV) among three Ln (III) elements. The separation factor (SF) values of Th (IV) to lanthanum (La) (III), europium (Eu) (III), and lutetium (Lu) (III) were SF Th/La = 114.41, SF Th/Eu = 52.75, and SF Th/Lu = 107.81, respectively. Graphical abstract Unlabelled Image • 1Dimensional-porous graphene oxide aerogel was established using polyethylenimine as the cross-linking and functionalizing agent. • The adsorbent possesses high selectivity arising from the dimensional-porous structure, the introduced binding sites, and the high hydrophilicity. • The adsorptive performance of the adsorbent showed a sensitively dependent relationship on the beginning mass ratio of polyethylenimine/graphene oxide. • A density functional theory simulation was performed, proving the adsorption complex of thorium possessed the lowest energy. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) emitters in the long wavelength region usually suffer from severe nonradiative decay according to the energy-gap law, and show relatively large energy split (ΔE ST) between the lowest singlet and triplet excited states which compromise efficient up-conversion. Here, we report three orange and red TADF emitters comprising 5, 10-disubstituted phenazine electron-donor and quinoxaline-derived electron-acceptors, which show excellent TADF properties and yield efficient organic light-emitting diodes (OLEDs). These symmetrical acceptor-donor-acceptor (A-D-A) type and rodlike molecules concurrently exhibit high photoluminescence quantum yields up to 85% and fast reverse intersystem crossing. Experimental and theoretical studies reveal that these excellent photophysical properties are attributed the synergistic effect of structural rigidity, steric hindrance and strength of the donor and acceptor units. Doped OLEDs based on these emitters achieved high maximum external electroluminescence quantum efficiencies up to 19.9%, and maximum luminance surpassing 31240 cd/m2. [Display omitted] • Highly efficient orange to red TADF emitters with high PLQYs (up to 85%) and short TADF lifetimes. • Tiny S 1 -T 1 energy splits and fast spin-flip due to rational molecular design and excited-state regulation. • High-performance OLED with EQE nearly 20%. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials with through-space charge transfer (TSCT) have recently attracted extensive attention. However, how to rationally design high-performance TSCT-TADF emitters with small ΔE ST , high photoluminescence quantum yields (PLQYs) and high stability remains challenging. Herein, two triptycene-derived TADF molecules bearing ortho-donor (D)-acceptor (A) conformations are designed and characterized. These emitters exhibit unique V-shaped face-to-face D-A alignments with significant intramolecular D-A interactions, which mediate TSCT between the D and A moieties in addition to the through-bond charge transfer (TBCT) and facilitate realizing small ΔE ST and high efficiencies. Meanwhile, the rigid 3D triptycene scaffold endows the emitters with excellent thermal stability and high film-formation quality. These TADF emitters exhibit small ΔE ST of 6.7 and 10.8 meV and high photoluminescence quantum yields of 0.80 and 0.40 in doped films, respectively. The doped OLEDs employing these emitters achieve high external quantum efficiencies up to 20.5%. [Display omitted] • 3D triptycene scaffold based TADF emitters with photoluminescent efficiency up to 80%. • V-shaped face-to-face D-A conformation for constructing through-space charge transfer (TSCT) pathway. • High performance OLED with EQE beyond 20%. [ABSTRACT FROM AUTHOR]

Abstract: The shape of a frustum is a bivariate function of aspect ratio (w) and base radii ratio (c). To investigate the shape influences on the packing density of frustums, random packings of cones (c =0), truncated cones and cylinders (c =1) with various heights and diameters are studied through numerical simulations. An improved relaxation algorithm with assembly sphere models for non-spherical particles is applied in the numerical simulations, and the randomness of the packings of the frustums considered is verified. Base on the simulation results, the relationship between the packing density and shape parameters is illustrated, and an empirical formula is proposed to reflect the correlation. It shows that, for the particles having the same w, truncated cones can be packed denser than cones, but looser than cylinders. The packing density of truncated cones first increases and then decreases with the growth of w, while the packing density increases monotonically with the increase of c. No obvious peak is found on the curve of packing density versus c for the random packing of truncated cones, which is different from the reported results for ordered packing where a peak was identified. Furthermore, we observe that the packing density of truncated cones is a linear superposition of the c effect on w effect, and the effects of c and w on the packing density can be treated independently. The optimal aspect ratios of truncated cones, which give the highest packing densities, are all around 0.8. The highest packing densities of cylinders and cones are also the upper and lower bound of the random packing density of truncated cones. [Copyright &y& Elsevier]

[Display omitted] • DGA-functionalized MIL-101 crystalline adsorbent was first synthesized. • Eu(III) was separated first from other rare earth elements. • The adsorption order of rare earth was changed compared with traditional adsorbents. • The separation coefficient β (Eu(III) / other rare earth) reached 53.055. • Eu(III) can be separated from interfering ions in the simulation of leaching solution. In this paper, a novel crystalline adsorbent MIL-101-DGA (DGA: Diglycolic Anhydride) is synthesized, which can change the order of traditional rare earth separation. This study is different from previously rare earth separation materials in which it can separate europium (III) first from other rare earth ions. The experiments result show that the separation coefficient (β) of preferentially separated europium (III) and other rare earth ions could reach 53.055, and the maximum adsorption capacity in the experiment was 33 mg/g. Density functional theory was used to calculate the absolute hardness of MIL-101-DGA from the perspective of hard-soft-acid-base theory, which explained the selective adsorption mechanism. Using MIL-101-DGA as an adsorbent, it can effectively recover Eu from the metal impurities Al, Ca, Cu, Mn, Zn and Y from the simulated phosphor leaching solution and has excellent recyclability. In summary, we believe that MIL-101-DGA is a new type of adsorbent that can effectively separate europium from rare earth and transition metal ions. [ABSTRACT FROM AUTHOR]