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Warner Oconnor posted an update 8 months, 1 week ago
Our studies demonstrate that azolate MOFs, such as Fe2(bdp)3 (bdp2- = 4,4′-(1,4-phenylene)bis(pyrazolate)), generally possess excellent chemical stabilities under myriad conditions. In addition, we find that carboxylate and salicylate frameworks possess complementary stabilities, with carboxylate MOFs possessing superior robustness toward acids, electrophiles, and oxidants, and salicylate MOFs demonstrating improved robustness toward bases, nucleophiles, and reductants. The guidelines provided herein should facilitate the rational design of robust frameworks for applications in synthetic chemistry and guide the development of new strategies for the postsynthetic modification of MOFs as well.Globally, over 200 million people are chronically exposed to arsenic (As) and/or manganese (Mn) from drinking water. We used machine-learning (ML) boosted regression tree (BRT) models to predict high As (>10 μg/L) and Mn (>300 μg/L) in groundwater from the glacial aquifer system (GLAC), which spans 25 states in the northern United States and provides drinking water to 30 million people. Stem Cells activator Our BRT models’ predictor variables (PVs) included recently developed three-dimensional estimates of a suite of groundwater age metrics, redox condition, and pH. We also demonstrated a successful approach to significantly improve ML prediction sensitivity for imbalanced data sets (small percentage of high values). We present predictions of the probability of high As and high Mn concentrations in groundwater, and uncertainty, at two nonuniform depth surfaces that represent moving median depths of GLAC domestic and public supply wells within the three-dimensional model domain. Predicted high likelihood of anoxic condition (high iron or low dissolved oxygen), predicted pH, relative well depth, several modeled groundwater age metrics, and hydrologic position were all PVs retained in both models; however, PV importance and influence differed between the models. High-As and high-Mn groundwater was predicted with high likelihood over large portions of the central part of the GLAC.Exploiting precious-metal-free and high-activity oxygen evolution reaction (OER) electrocatalysts has been in great demands toward many energy storage and conversion processes, for example, carbon dioxide reduction, metal-air batteries, and water splitting. In this study, the simple solid-state method is employed for coupling Ni (electron donors) with lower-Fermi-level MoO2 or WOx (electron acceptors) into donor-acceptor ensembles with well-designed interfaces as robust electrocatalysts for OER. The resulting Ni/MoO2 and Ni/WOx electrocatalysts exhibit smaller overpotentials of 287 and 333 mV at 10 mA cm-2 as well as smaller Tafel slopes of 51 and 65 mV/dec, respectively, with respect to the single Ni, MoO2, WOx, and even the benchmark RuO2 in 1 M KOH. Specially, on account of a higher Fermi level of Ni in comparison with MoO2 and WOx, their strong electronic interaction results in directional interfacial electron transfer and increases the hole density over Ni, dramatically enriching the population of high-valence Ni3+ active sites and decreasing the Fermi level of Ni. The existence of Ni3+ can strengthen the chemisorption of OH-, and the downshift of the Ni Fermi level can significantly expedite migration of electrons toward the surface of catalysts during OER, thus synergistically boosting the OER catalytic performance. Furthermore, the inner Ni/MoO2 and Ni/WOx heterostructures and the electrochemically induced surface layers of oxides/hydroxides collectively boost the OER kinetics. This study highlights the importance of designing highly efficient OER electrocatalysts with high-valence active species (Ni3+) and better matched energy levels induced by the work function difference through interfacial engineering.Rapid and inexpensive serological tests for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibodies are essential to conduct large-scale seroprevalence surveys and can potentially complement nucleic acid or antigen tests at the point of care. During the COVID-19 pandemic, extreme demand for traditional lateral flow tests has stressed manufacturing capacity and supply chains. Motivated by this limitation, we developed a SARS-CoV-2 antibody test using cellulose, an alternative membrane material, and a double-antigen sandwich format. Functionalized SARS-CoV-2 antigens were used as both capture and reporter binders, replacing the anti-human antibodies currently used in lateral flow tests. The test could provide enhanced sensitivity because it labels only antibodies against SARS-CoV-2 and the signal intensity is not diminished due to other human antibodies in serum. Three-dimensional channels in the assay were designed to have consistent flow rates and be easily manufactured by folding wax-printed paper. We demonstrated that this simple, vertical flow, cellulose-based assay could detect SARS-CoV-2 antibodies in clinical samples within 15 min, and the results were consistent with those from a laboratory, bead-based chemiluminescence immunoassay that was granted emergency use approval by the US FDA.The practical deployment of advanced Li-S batteries is severely constrained by the uncontrollable lithium polysulfide conversion under realistic conditions. Although a plethora of advanced sulfur hosts and electrocatalysts have been examined, the fundamental mechanisms are still elusive and predictive design approaches have not yet been established. Here, we examined a series of well-defined Fe-N-C sulfur hosts with systematically varied and strongly coupled Fe3C and Fe electrocatalysts, prepared by one-step pyrolysis of a novel Fexy/polypyrrole composite at different temperatures. We revealed the key roles of Fe3C and metallic Fe on modulating polysulfide conversion, in that the polar Fe3C strongly adsorbs polysulfide whereas the Fe particles catalyze fast polysulfide conversion. We then highlight the superior performance of the rational host with strongly coupled Fe3C and Fe on mesoporous Fe-N-C host on promoting nearly complete polysulfide conversion, especially for the challenging short-chain Li2S4 conversion to Li2S.
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