We develop an N-coordination strategy to design a robust CO reduction reaction (CORR) electrocatalyst with atomically dispersed Co-N site anchored on polymer-derived hollow N-doped porous carbon spheres. Our catalyst exhibits high selectivity for CORR with CO Faradaic efficiency (FE) above 90% over a wide potential range from -0.57 to -0.88 V (the FE exceeded 99% at -0.73 and -0.79 V). The CO current density and FE remained nearly unchanged after electrolyzing 10 h, revealing remarkable stability. Experiments and density functional theory calculations demonstrate single-atom Co-N site is the dominating active center simultaneously for CO activation, the rapid formation of key intermediate COOH* as well as the desorption of CO.

Monolayer phosphorene provides a unique two-dimensional (2D) platform to investigate the fundamental dynamics of excitons and trions (charged excitons) in reduced dimensions. However, owing to its high instability, unambiguous identification of monolayer phosphorene has been elusive. Consequently, many important fundamental properties, such as exciton dynamics, remain underexplored. We report a rapid, noninvasive, and highly accurate approach based on optical interferometry to determine the layer number of phosphorene, and confirm the results with reliable photoluminescence measurements. Furthermore, we successfully probed the dynamics of excitons and trions in monolayer phosphorene by controlling the photo-carrier injection in a relatively low excitation power range. Based on our measured optical gap and the previously measured electronic energy gap, we determined the exciton binding energy to be ,0.3 eV for the monolayer phosphorene on SiO 2 /Si substrate, which agrees well with theoretical predictions. A huge trion binding energy of ,100 meV was first observed in monolayer phosphorene, which is around five times higher than that in transition metal dichalcogenide (TMD) monolayer semiconductor, such as MoS 2 . The carrier lifetime of exciton emission in monolayer phosphorene was measured to be ,220 ps, which is comparable to those in other 2D TMD semiconductors. Our results open new avenues for exploring fundamental phenomena and novel optoelectronic applications using monolayer phosphorene. Keywords: exciton; monolayer phosphorene; optical injection; two-dimensional materials INTRODUCTION Phosphorene is a recently developed two-dimensional (2D) material that has attracted tremendous attention owing to its unique anisotropic manner 1-6 , layer-dependent direct band gaps 7,8 , and quasi-onedimensional (1D) excitonic nature 9,10 , which are all in drastic contrast with the properties of other 2D materials, such as graphene 11 and transition metal dichalcogenide (TMD) semiconductors [12][13][14] . Monolayer phosphorene has been of particular interest in exploring technological applications and investigating fundamental phenomena, such as 2D quantum confinement and many-body interactions 9,15 . However, such unique 2D materials are unstable in ambient conditions and degrade quickly 8,16 . Particularly, monolayer phosphorene is expected to be much less stable than few-layer phosphorene 16 , hence making its identification and characterization extremely challenging. There is a huge controversy on the identification of very few-layer (one or two layers) phosphorene and thus on their properties [16][17][18] . This controversy was primarily due to the lack of a robust experimental technique to precisely identify the monolayer phosphorene. Consequently, many important fundamental properties of monolayer phosphorene, such as its excitonic nature, remain elusive. In this study, we propose and implement a rapid, noninvasive,

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The organized assembly of particles into superstructures is typically governed by specific molecular interactions or external directing factors associated with the particle building blocks, both of which are particle-dependent. These superstructures are of interest to a variety of fields because of their distinct mechanical, electronic, magnetic and optical properties. Here, we establish a facile route to a diverse range of superstructures based on the polyphenol surface-functionalization of micro- and nanoparticles, nanowires, nanosheets, nanocubes and even cells. This strategy can be used to access a large number of modularly assembled superstructures, including core-satellite, hollow and hierarchically organized supraparticles. Colloidal-probe atomic force microscopy and molecular dynamics simulations provide detailed insights into the role of surface functionalization and how this facilitates superstructure construction. Our work provides a platform for the rapid generation of superstructured assemblies across a wide range of length scales, from nanometres to centimetres.

The electrochemical direct synthesis of hydrogen peroxide (H 2 O 2 ) is significant but still challenging because of the lack of highly selective and active catalysts. Here, we report the synthesis of hollow nanospheres constructed by atomically dispersing platinum in amorphous CuS x support (h-Pt 1 -CuS x ) with a high concentration of single atomic Pt sites (24.8 at%), and this catalyst can consistently reduce O 2 into H 2 O 2 with selectivity of 92%-96% over a wide potential range of 0.05-0.7 V versus RHE in HClO 4 electrolyte. Scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomically isolated form of Pt with a low valance of +0.75. An electrochemical device that can synthesize H 2 O 2 directly from H 2 and O 2 is fabricated with H 2 O 2 productivity as high as 546 G 30 mol kg cat À1 h À1 . The well-defined and high-concentration single atomic Pt sites result in ultrahigh productivity of H 2 O 2 .

Nematode parasitism is a worldwide health problem resulting in malnutrition and morbidity in over 1 billion people. The molecular mechanisms governing infection are poorly understood. Here, we report that an evolutionarily conserved nuclear hormone receptor signaling pathway governs development of the stage 3 infective larvae (iL3) in several nematode parasites, including Strongyloides stercoralis, Ancylostoma spp., and Necator americanus. As in the free-living Caenorhabditis elegans, steroid hormone-like dafachronic acids induced recovery of the dauer-like iL3 in parasitic nematodes by activating orthologs of the nuclear receptor DAF-12. Moreover, administration of dafachronic acid markedly reduced the pathogenic iL3 population in S. stercoralis, indicating the potential use of DAF-12 ligands to treat disseminated strongyloidiasis. To understand the pharmacology of targeting DAF-12, we solved the 3-dimensional structure of the S. stercoralis DAF-12 ligand-binding domain cocrystallized with dafachronic acids. These results reveal the molecular basis for DAF-12 ligand binding and identify nuclear receptors as unique therapeutic targets in parasitic nematodes.dafachronic acid ͉ parasitology ͉ pharmacology ͉ X-ray crystal structure P arasitic nematodes constitute a large family of pathogens that infect hosts ranging from plants and animals to people, causing great economic loss and worldwide health threats (1, 2). One of the most problematic parasites, Strongyloides stercoralis, is estimated to infect 100-200 million people. Primary infections are often asymptomatic and clinically silent in immunocompetent individuals. However, once the immune system is compromised (e.g., by corticosteroid therapy), the parasite establishes autoinfection cycles that result in a frequently fatal disseminated strongyloidiasis (3, 4). Hookworms (Ancylostoma and Necator spp.) are other parasitic nematodes that affect Ͼ1 billion people and are the dominant cause for iron-deficient anemia worldwide (2). Oral administration of anthelmintics such as benzimidazoles (microtuble toxins) and ivermectin (a neurotoxin) is currently the preferred treatment for nematode infections (5). However, no reliable options exist for treating the more severe form of disseminated strongyloidiasis (6). Moreover, resistance to the anthelmintics has become widespread in animals and is beginning to occur in humans (2, 7). Therefore, studying the mechanisms that govern nematode life cycles is an attractive approach to identifying new therapeutic targets.Infection of hosts by parasitic nematodes is mediated by infective larvae, which in S. stercoralis and hookworm are the third stage or L3 larvae (iL3) (4, 5). Interestingly, iL3 larvae resemble the dauer larvae of the free-living nematode Caenorhabditis elegans in that they are all nonfeeding, developmentally arrested, dormant filariform larvae with a sealed buccal capsule and thickened body wall cuticle, enabling them to survive environmental challenges (8). Like C. elegans dauer larvae, iL3 recover from their ar...

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