Highly Stretchable Polyurethane Porous Membranes with Adjustable Morphology for Advanced Lithium Metal Batteries.

A highly flexible, tunable morphology membrane with excellent thermal stability and ionic conductivity can endow lithium metal batteries with high power density and reduced dendrite growth. Herein, a porous Polyurethane (PU) membrane with an adjustable morphology was prepared by a simple nonsolvent-induced phase separation technique. The precise control of the final morphology of PU membranes can be achieved through appropriate selection of a nonsolvent, resulting a range of pore structures that vary from finger-like voids to sponge-like pores. The implementation of combinatorial DFT and experimental analysis has revealed that spongy PU porous membranes, especially PU-EtOH, show superior electrolyte wettability (472%), high porosity (75%), good mechanical flexibility, robust thermal dimensional stability (above 170 °C), and elevated ionic conductivity (1.38 mS cm-1) in comparison to the polypropylene (PP) separator. The use of PU-EtOH in Li//Li symmetric cell results in a prolonged lifespan of 800 h, surpasing the longevity of PU or PP cells. Moreover, when subjected to a high rate of 5 C, the LiFePO4/Li half-cell with a PU-EtOH porous membrane displayed better cycling performance (115.4 mAh g-1) compared to the PP separator (104.4 mAh g-1). Finally, the prepared PU porous membrane exhibits significant potential for improving the efficiency and safety of LMBs.

Contact evaluation of the penta-PdPSe/graphene vdW heterojunction: tuning the Schottky barrier and optical properties.

In this work, we design a van der Waals heterojunction composed of semiconducting penta-PdPSe and semi-metallic graphene (G) monolayers based on state-of-the-art theoretical calculations. Our results show that both monolayers well preserve their intrinsic features and possess an n-type near Ohmic Schottky contact with a low Schottky barrier height of 0.085 eV for the electrons at the vertical interface. The electronic band alignment suggests a negative band bending of -1.47 eV at the lateral interface, implying electrons as the major transport carriers. Moreover, the transmission gap closely mirrors the heterojunction's band gap, indicating a subtle yet profound interaction between graphene and penta-PdPSe monolayers, which leads to enhanced optical absorption coefficient reaching 106 cm-1 and strong conductivity spanning the visible to ultraviolet region. In addition, our study demonstrates the ability to modify the penta-PdPSe/G heterojunction interface, switching between p-type as well as Ohmic contacts by applying external electric fields. These properties render the penta-PdPSe/G heterojunction promising for optoelectronic applications.

Enhanced As-COF nanochannels as a high-capacity anode for K and Ca-ion batteries.

Covalent organic frameworks can be used for next-generation rechargeable metal-ion batteries due to their controllable spatial and chemical architectures and plentiful elemental reserves. In this study, the arsenic-based covalent organic framework (As-COF) is designed by employing the geometrical symmetry of a semiconducting phosphazene-based covalent organic framework that uses p-phenylenediamine as a linker and hexachorocyclotriphosphazene as an As-containing monomer in a C3-like spatial configuration. The As-COF with engineered nanochannels demonstrates exceptional anodic behavior for potassium (K) and calcium (Ca) ion batteries. It exhibits a high storage capacity of about 914(2039) mA h g-1, low diffusion barriers of 0.12(0.26) eV, low open circuit voltage of 0.23(0.18) V, and a minimal volume expansion of 2.41(2.32)% for K (Ca) ions. These attributes collectively suggest that As-COF could significantly advance high-capacity rechargeable batteries.

Mechanistic Studies on Aluminum-Catalyzed Ring-Opening Alternating Copolymerization of Maleic Anhydride with Epoxides: Ligand Effects and Quantitative Structure-Activity Relationship Model.

Previous work has indicated that aluminum (Al) complexes supported by a bipyridine bisphenolate (BpyBph) ligand exhibit higher activity in the ring-opening copolymerization (ROCOP) of maleic anhydride (MAH) and propylene oxide (PO) than their salen counterparts. Such a ligand effect in Al-catalyzed MAH-PO copolymerization reactions has yet to be clarified. Herein, the origin and applicability of the ligand effect have been explored by density functional theory, based on the mechanistic analysis for chain initiation and propagation. We found that the lower LUMO energy of the (BpyBph)AlCl complex accounts for its higher activity than the (salen)AlCl counterpart in MAH/epoxide copolymerizations. Inspired by the ligand effect, a structure-energy model was further established for catalytic activity (TOF value) predictions. It is found that the LUMO energies of aluminum chloride complexes and their average NBO charges of coordinating oxygen atoms correlate with the catalytic activity (TOF value) of Al complexes (R2 value of 0.98 and '3-fold' cross-validation Q2 value of 0.88). This verified that such a ligand effect is generally applicable in anhydride/epoxide ROCOP catalyzed by aluminum complex and provides hints for future catalyst design.

Mechanistic Study on Steric Activity Interplay of Olefin/Polar Monomers for Industrially Selective Late Transition Metal Catalytic Reactions.

A significant issue in developing metal-catalyzed plastic polymer materials is obtaining distinctive catalytic characteristics to compete with current plastics in industrial commodities. We performed first-principle DFT calculations on the key insertion steps for industrially important monomers, vinyl fluoride (VF) and 3,3,3-trifluoropropene (TFP), to explain how the ligand substitution patterns affect the complex's polymerization behaviors. Our results indicate that the favorable 2,1-insertion of TFP is caused by less deformation in the catalyst moiety of the complexes in contrast to the 1,2-insertion mode. In contrast to the VF monomer, the additional interaction between the fluorine atoms of 3,3,3-trifluoropropene and the carbons of the catalyst ligands also contributed to favor the 2,1-insertion. It was found that the regioselectivity of the monomer was predominated by the progressive alteration of the catalytic geometry caused by small dihedral angles that were developed after the ligand-monomer interaction. Based on the distribution of the 1,2- and 2,1-insertion products, the activity and selectivity were influenced by the steric environment surrounding the palladium center; thus, an increased steric bulk visibly improved the selectivity of the bulkier polar monomer (TFP) during the copolymerization mechanism. In contrast, better activity was maintained through a sterically less hindered Pd metal center; the calculated moderate energy barriers showed that a catalyst with less steric hindrance might provide an opportunity for a wide range of prospective industrial applications.

Tunable metalensing based on plasmonic resonators embedded on thermosresponsive hydrogel.

Metalenses of adjustable power and ultrathin flat zoom lens system have emerged as a promising and key photonic device for integrated optics and advanced reconfigurable optical systems. Nevertheless, realizing an active metasurface retaining lensing functionality in the visible frequency regime has not been fully explored to design reconfigurable optical devices. Here, we present a focal tunable metalens and intensity tunable metalens in the visible frequency regime through the control of the hydrophilic and hydrophobic behavior of freestanding thermoresponsive hydrogel. The metasurface is comprised of plasmonic resonators embedded on the top of hydrogel which serves as dynamically reconfigurable metalens. It is shown that the focal length can be continuously tuned by adjusting the phase transition of hydrogel, the results reveal that the device is diffraction limited in different states of hydrogel. In addition, the versatility of hydrogel-based metasurfaces is further explored to design intensity tunable metalens, that can dynamically tailor the transmission intensity and confined it into the same focal spot under different states, i.e., swollen and collapsed. It is anticipated that the non-toxicity and biocompatibility make the hydrogel-based active metasurfaces suitable for active plasmonic devices with ubiquitous roles in biomedical imaging, sensing, and encryption systems.

Mechanistic study to reveal steric and electronic aspects involved in the formation of microstructures during Pd-catalyzed olefin/divinyl formal copolymerization: reactivity to catalyst choice.

The advancement of metal-catalyzed copolymers is a formidable challenge for achieving distinct catalytic properties to compete with existing plastic polymers in industrial commodities. Herein, we reveal the roles of electronic and steric environments in the thermodynamic preference of microstructures in ethylene/divinyl formal (DVF) co-polymerization using a Pd catalyst under mild conditions to accommodate the respective industrial applicabilities. The insertion products of DVF result in the alteration of the steric crowding, ultimately favoring the efficient formation of cyclic units having potential applications in the manufacture of high-strength fibers. More specifically, to achieve an improved yield of the end copolymer, we tuned the catalytic activity and regioselectivity through a variety of catalysts during ethylene-DVF co-polymerization. The naphthalene-bridged (P^O)PdMe catalyst was found to be promising in terms of the least hindered (buried volume of 47.8%) environment with the thermodynamic preference of 2,1-insertion with an energy of 5.1 kcal mol-1 among all the Pd-metal based catalysts. The highest activity with moderate energy barriers of the proposed catalyst will open new avenues for achieving a variety of potential applications, which is typically not possible using existing polymerization techniques.

Poly(ether imide) Porous Membrane Developed by a Scalable Method for High-Performance Lithium-Sulfur Batteries: Combined Theoretical and Experimental Study.

Lithium-sulfur (Li-S) batteries are one of the emerging candidates for energy storage systems due to their high theoretical energy density and the abundance/nontoxicity/low cost of sulfur. Compared with conventional lithium-ion batteries, multiple new challenges have been brought into this advanced battery system, such as polysulfide shuttling in conventional polyolefin separators and undesired lithium dendrite formation of the Li metal anode. These issues severely affect the cell performance and impede their practical applications. Herein, we develop a poly(ether imide) (PEI)-based membrane with a sponge-like pore morphology as the separator for the Li-S battery by a simplified phase inversion method. This new separator can not only alleviate the new challenges in Li-S batteries but also exhibit excellent ion conductivity, better thermal stability, and higher mechanical strength compared to those of the conventional polypropylene (PP) separator. A combined experimental and theoretical study indicates that the sponge-like morphology of the PEI membrane and its good wettability toward the electrolyte can facilitate uniform ion transportation and suppress dendrite growth. Meanwhile, the PEI molecules exhibit a strong interaction with polysulfides and avoid their shuttling effectively. As a result, the PEI-based Li-S battery shows a much better performance from various aspects (capacity, rate capability, and cycling stability) than that of the PP-based Li-S battery, especially at high charge/discharge current densities and high sulfur loadings. Since the developed PEI membrane can be easily scaled up, this work may accelerate the practical applications of Li-S batteries from the point of separators.

Bridging 1D Inorganic and Organic Synthesis to Fabricate Ultrathin Bismuth-Based Nanotubes with Controllable Size as Anode Materials for Secondary Li Batteries.

The growth of ultrathin 1D inorganic nanomaterials with controlled diameters remains challenging by current synthetic approaches. A polymer chain templated method is developed to synthesize ultrathin Bi2 O2 CO3 nanotubes. This formation of nanotubes is a consequence of registry between the electrostatic absorption of functional groups on polymer template and the growth habit of Bi2 O2 CO3 . The bulk bismuth precursor is broken into nanoparticles and anchored onto the polymer chain periodically. These nanoparticles react with the functional groups and gradually evolve into Bi2 O2 CO3 nanotubes along the chain. 5.0 and 3.0 nm tubes with narrow diameter deviation are synthesized by using branched polyethyleneimine and polyvinylpyrrolidone as the templates, respectively. Such Bi2 O2 CO3 nanotubes show a decent lithium-ion storage capacity of around 600 mA h g-1 at 0.1 A g-1 after 500 cycles, higher than other reported bismuth oxide anode materials. More interestingly, the Bi materials developed herein still show decent capacity at very low temperatures, that is, around 330 mA h g-1 (-22 °C) and 170 mA h g-1 (-35 °C) after 75 cycles at 0.1 A g-1 , demonstrating their promising potential for practical application in extreme conditions.

Mechanistic Studies for Palladium Catalyzed Copolymerization of Ethylene with Vinyl Ethers.

The mechanism of ethylene with vinyl ether (VE, CH2=CHOEt) copolymerization catalyzed by phosphine-sulfonate palladium complex (A) was investigated by density functional theory (DFT) calculation. On achieving an agreement between theory and experiment, it is found that the favorable 1,2-selective insertion of VE into the complex A originates from stronger hydrogen interaction between the oxygen atom of VE and the ancillary ligand of catalyst A. Additionally, VE insertion is easier into the ethylene pre-inserted intermediate than that into the catalyst to form the resultant copolymers with the major units of OEt in chain and minor units of OEt at the chain end. The effect of ß-OEt and ß-H elimination was explored to elucidate chain termination and the molecular weight of copolymers. Furthermore, a family of cationic catalysts has been demonstrated to copolymerize ethylene with VE along with our modified cationic complex B with higher incorporation of VE and reactivity in comparison with complex A, which was modelled computationally by increasing the strong interactions between the catalyst and monomer moiety. Other than VE, the activity of cationic complex B for copolymerization of vinyl chloride and methacrylate is also computed successfully.

Human Health Risk Assessment by Dietary Intake and Spatial Distribution Pattern of Polybrominated Diphenyl Ethers and Dechloran Plus from Selected Cities of Pakistan.

A class of intractable bio accumulative halogenated compounds polybrominated diphenyl ethers (PBDEs) was studied. Specifically, PBDEs and dechloran plus (DP) contamination in wheat and the assaulted environment-agricultural soil and dust-from metropolitan cities of Pakistan was the focus. The exposure of brominated flame retardants (BFRs) to humans, their probable toxicological impact on health, source apportionment, and the spatial tendency of BFRs were studied. Chromatographic analysis was performed, and concentrations (ng g-1) of ΣPBDE and ΣDP in soil, dust, and cereal crops were estimated in a range from 0.63 to 31.70 n.d. to 6.32 and n.d. to 3.47, respectively, and 0.11 to 7.05, n.d. to 4.56 and 0.05 to 4.95, respectively. Data analysis of source apportionment reflected that the existence of solid and e-waste sites, long-range transport, urban and industrial fraction can be the potential source of PBDE and DP pollution. Moreover, potential hazardous risks to human health across the study area via the dietary intake of cereal foods were deemed trifling, and were gauged on the basis of existing toxicological data.

Spatial distribution of heavy metals in crops in a wastewater irrigated zone and health risk assessment.

Industrialization and urbanization have produced a large amount of wastewater. Part of the municipal wastewater has been used as an irrigation source in urban/suburban areas. Its utilization, although economically beneficial, can significantly deteriorate the integrity of the ecological systems (e.g., in terms of quality of soil and resulting food products). The objectives of this study are to investigate the spatial distribution and bio-accumulation of heavy metals (e.g., Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) in food crops (and topsoil) and associated health risks of their consumption in the area of Mangla Dam, Pakistan. To this end, studies were conducted to assess the risk factors such as the bioconcentration factor (BCF), health risk index (HRI), and daily intake of heavy metals (DIM). Accordingly, there was more contamination in Mangla Dam water irrigated zone (DWI) than in the groundwater irrigated zone (GWI). Co exhibited the maximum BCF of 7.45 for Eruca sativa and 6.61 for Brassica campestris in the GWI zone. Likewise, enhanced risk to human health was seen from of Cd, Cr, and Pb in Triticum aestivum and Eruca sativa grown in the DWI zone. It is recommended that the quality profile of wastewater discharge into freshwater ecosystems should be continuously monitored and regulated.

Polychlorinated biphenyl (PCBs) in rice grains and straw; risk surveillance, congener specific analysis, distribution and source apportionment from selected districts of Punjab Province, Pakistan.

The current study presents health risk surveillance by investigating the levels of polychlorinated biphenyls (PCBs) in rice (Oryza sativa L.) grains and rice straw. Samples were collected from four districts (Okara, Sahiwal, Lahore and Sheikhpura) of Punjab Province, Pakistan for congener specific analysis of PCBs, and to observe the spatial distribution pattern and point sources. Level of Σ30 PCB (ng g(-1)) in rice grains and rice straw ranged from 4.31 to 29.68 and 6.11-25.35, respectively. Tetra-CBs were found predominant in rice straw (49%) and grains (38%) over other PCB homologs. No significant variation (P>0.005) was observed for most of the screened PCBs congeners except, PCB-66, -77, -60, -101, -74, -138, -153 and -105 in rice grains and PCB-66 in rice straw. Reported toxicity equivalency (TEQ) values for dioxin like PCBs in rice grains were found lower than the previously published reports from Asian countries, however higher TEQ values are reported for rice straw in this study. Health was found at risk of cancer among one in million by consumption of the study area food stuffs, though no considerable carcinogenic risks to human health was found.

Human health risk assessment, congener specific analysis and spatial distribution pattern of organochlorine pesticides (OCPs) through rice crop from selected districts of Punjab Province, Pakistan.

To evaluate the screening level risk assessment of OCPs in rice (Oryza sativa L.) straw (n=20) and rice grains (n=20), samples were collected from different districts of Punjab Province, Pakistan. ∑OCPs' levels (ng g(-1)) in rice straw and grains ranged from 3.63 to 39.40, 2.72 to 49.89, respectively. DDTs were found predominant over the other detected OCP isomers followed by HCH and heptachlor. Results of one way ANOVA reflected no significant difference for OCPs' levels among sampling sites, except heptachlor for rice grains. ∑OCPs' concentration in rice straw samples was exceeding the minimal residual levels (MRLs) (Australian and Japanese). Results of dietary intake and risk assessment suggested that rice straw is not safe for animals to consume as fodder. Human health was suggested to have some carcinogenic risks by consumption of rice grains, however, no considerable hazardous risk (non-carcinogenic) to human health was found.