Triggering Pt Active Sites in Basal Plane of Van der Waals PtTe2 Materials by Amorphization Engineering for Hydrogen Evolution.

Exposing active sites and optimizing their bonding strength to reaction intermediates are two essential strategies to significantly improve the catalytic performance of two-dimensional (2D) materials. However, pursuing an efficient way to achieve these goals simultaneously remains a considerable challenge. Here, using 2D PtTe2 van der Waals material with well-defined crystal structure and atomically thin thickness as a model catalyst, we observe that a moderate calcination strategy can promote the structural transformation of 2D crystal PtTe2 nanosheets (c-PtTe2 NSs) into oxygen-doped 2D amorphous PtTe2 NSs (a-PtTe2 NSs). The experimental and theoretical investigations cooperatively reveal that oxygen dopants can break the inherent Pt-Te covalent bond in c-PtTe2 NSs, thereby triggering the reconfiguration of interlayer Pt atoms and exposing them thoroughly. Meanwhile, the structural transformation can effectively tailor the electronic properties (e.g., the density of state near the Fermi level, d-band center, and conductivity) of Pt active sites via the hybridization of Pt 5d orbitals and O 2p orbitals. As a result, a-PtTe2 NSs with large amounts of exposed Pt active sites and optimized binding strength to hydrogen intermediates exhibit excellent activity and stability in hydrogen evolution reaction. This article is protected by copyright. All rights reserved.

Electrocatalytically Activating and Reducing N2 Molecule by Tuning Activity of Local Hydrogen Radical.

Decarbonizing N2 conversion is particularly challenging, but essential for sustainable development of industry and agriculture. Herein, we achieve electrocatalytic activation/reduction of N2 on X/Fe-N-C (X=Pd, Ir and Pt) dual-atom catalysts under ambient condition. We provide solid experimental evidence that local hydrogen radical (H*) generated on the X site of the X/Fe-N-C catalysts can participate in the activation/reduction of N2 adsorbed on the Fe site. More importantly, we reveal that the reactivity of X/Fe-N-C catalysts for N2 activation/reduction can be well adjusted by the activity of H* generated on the X site, i.e., the interaction between the X-H bond. Specifically, X/Fe-N-C catalyst with the weakest X-H bonding exhibits the highest H* activity, which is beneficial to the subsequent cleavage of X-H bond for N2 hydrogenation. With the most active H*, the Pd/Fe dual-atom site promotes the turnover frequency of N2 reduction by up to 10 times compared with the pristine Fe site.

Catalytically active atomically thin cuprate with periodic Cu single sites.

Rational design and synthesis of catalytically active two-dimensional (2D) materials with an abundance of atomically precise active sites in their basal planes remains a great challenge. Here, we report a ligand exchange strategy to exfoliate bulk [Cu4(OH)6][O3S(CH2)4SO3] cuprate crystals into atomically thin 2D cuprate layers ([Cu2(OH)3]+). The basal plane of 2D cuprate layers contains periodic arrays of accessible unsaturated Cu(II) single sites (2D-CuSSs), which are found to promote efficient oxidative Chan-Lam coupling. Our mechanistic studies reveal that the reactions proceed via coordinatively unsaturated CuO4(II) single sites with the formation of Cu(I) species in the rate-limiting step, as corroborated by both operando experimental and theoretical studies. The robust stability of 2D-CuSSs in both batch and continuous flow reactions, coupled with their recyclability and good performance in complex molecule derivatization, render 2D-CuSSs attractive catalyst candidates for broad utility in fine chemical synthesis.

Ultrabroadband plasmon driving selective photoreforming of methanol under ambient conditions.

Liquid methanol has the potential to be the hydrogen energy carrier and storage medium for the future green economy. However, there are still many challenges before zero-emission, affordable molecular H2 can be extracted from methanol with high performance. Here, we present noble-metal-free Cu-WC/W plasmonic nanohybrids which exhibit unsurpassed solar H2 extraction efficiency from pure methanol of 2,176.7 µmol g-1 h-1 at room temperature and normal pressure. Macro-to-micro experiments and simulations unveil that local reaction microenvironments are generated by the coperturbation of WC/W's lattice strain and infrared-plasmonic electric field. It enables spontaneous but selective zero-emission reaction pathways. Such microenvironments are found to be highly cooperative with solar-broadband-plasmon-excited charge carriers flowing from Cu to WC surfaces for efficient stable CH3OH plasmonic reforming with C3-dominated liquid products and 100% selective gaseous H2. Such high efficiency, without any COx emission, can be sustained for over a thousand-hour operation without obvious degradation.

FOXM1 increases hTERT protein stability and indicates poor prognosis in gastric cancer.

Gastric cancer is one of most lethal diseases across the world. However, the underlying mechanism of gastric cancer carcinogenesis and development is still not fully known. Forkhead box M1 (FOXM1) belongs to the FOX family and has crucial roles in transactivation of multiple oncogenes in several cancer types, including gastric cancer. Recent studies have also shown the non-transcriptional function of FOXM1 via protein-protein interactions. Human telomerase reverse transcriptase (hTERT) is the core subunit of telomerase that facilitates cancer initiation and progression by maintaining cell immortalization, promoting cell proliferation and inhibiting cell apoptosis. However, the relationship between FOXM1 and hTERT in gastric cancer is still unclear. In our study, we found that FOXM1 and hTERT were convergent to the cell cycle-related pathways and they were positively related with advanced gastric cancer stages and poor outcomes. Simultaneous high levels of FOXM1 and hTERT predicted the worst prognosis. FOXM1 could increase hTERT protein rather than mRNA levels in a non-transcriptional manner. Mechanistically, FOXM1 interrupted the interaction between the E3 ligase MKRN1 and hTERT and decreased hTERT protein degradation. Further studies revealed that FOXM1 interacted with hTERT through its DNA-binding domain (DBD) region. Finally, we found that hTERT played important roles in FOXM1-mediated activation of the Wnt/ß-catenin pathway to promote gastric cancer cell proliferation. Taken together, we found a novel non-classical function of FOXM1 to increase hTERT protein stability. Targeting the FOXM1-hTERT pathway may be a potential therapeutic strategy in treating gastric cancer.

Realization of Oriented and Nanoporous Bismuth Chalcogenide Layers via Topochemical Heteroepitaxy for Flexible Gas Sensors.

Most van der Waals two-dimensional (2D) materials without surface dangling bonds show limited surface activities except for their edge sites. Ultrathin Bi2Se3, a topological insulator that behaves metal-like under ambient conditions, has been overlooked on its surface activities. Herein, through a topochemical conversion process, ultrathin nanoporous Bi2Se3 layers were epitaxially deposited on BiOCl nanosheets with strong electronic coupling, leading to hybrid electronic states with further bandgap narrowing. Such oriented nanoporous Bi2Se3 layers possessed largely exposed active edge sites, along with improved surface roughness and film forming ability even on inkjet-printed flexible electrodes. Superior room-temperature NO2 sensing performance was achieved compared to other 2D materials under bent conditions. Our work demonstrates that creating nanoscale features in 2D materials through topochemical heteroepitaxy is promising to achieve both favorable electronic properties and surface activity toward practical applications.

Helicobacter pylori infection induces stem cell-like properties in Correa cascade of gastric cancer.

Gastric cancer (GC) is the fourth leading cause of cancer-related death. Its poor prognosis is attributed to unclear pathogenesis. Currently, the most widely accepted model for elucidating the mechanism of GC is the Correa cascade, which covers several histological lesions of the gastric mucosa. GC stem cells (CSCs) are crucial for oncogenesis in the Correa cascade and GC progression. As Helicobacter pylori (H. pylori) is the etiological factor in the Correa cascade, growing evidence suggests that enhancement of gastric stem cell-like properties and increase in CSCs correlate with H. pylori infection. In this paper, we review recent studies that present pathogenic mechanisms by which H. pylori induces gastric stem cell-like properties and CSCs, which may supplement the existing Correa model of GC. First, the dysfunction of developmental signaling pathways associated with H. pylori infection leads to the enhancement of gastric stemness. Second, H. pylori infection promotes alteration of the gastric mucosal microenvironment. In addition, epithelial-mesenchymal transition (EMT) may contribute to H. pylori-induced gastric stemness. Taken together, understanding these pathogeneses will provide potential therapeutic targets for the treatment of CSCs and malignant GC in H. pylori induced-Correa cascade of GC.

The Effects of Behavioral Foundations and Business Strategy on Corporate Dividend Policy.

This study analyzes the influence of behavioral foundation factors and corporate strategic behavior on the formulation of corporate dividend policy. We use the Logit model and the OLS model for estimating the empirical model. The year- and industry-fixed effects are controlled in the model. We consider the behavioral foundations in three dimensions-ambiguity aversions, risk aversion, and loss aversion. The results show firms with high ambiguity or high risk infrequently pay dividends but firms with loss-averse behavior tend to pay dividends. This paper also provides evidence that a firms' business strategy influences its corporate dividend policy. Aggressive firms inhibit the payout of dividends. In additional tests, we find the results remain unchanged in those firms with high corporate governance or high growth opportunities.

Solvent-Free Preparation of Closely Packed MoS2 Nanoscrolls for Improved Photosensitivity.

Due to their enhanced light absorption efficiency, one-dimensional (1D) transition metal dichalcogenide (TMDC) nanoscrolls derived from two-dimensional (2D) TMDC nanosheets have shown excellent optoelectronic properties. Currently, organic solvent and alkaline droplet-assisted scrolling methods are popular for preparing TMDC nanoscrolls. Unfortunately, the adsorption of organic solvent or alkaline impurities on TMDC is inevitable during the preparation, which affects the optoelectronic properties of TMDC. In this work, we report a solvent-free method to prepare closely packed MoS2 nanoscrolls by dragging a deionized water droplet onto the chemical vapor deposition grown monolayer MoS2 nanosheets at 100 °C (referred to as MoS2 NS-W). The as-prepared MoS2 NS-W was well characterized by optical microscopy, atomic force microscopy, and ultralow frequency (ULF) Raman spectroscopy. After high temperature annealing, the height of MoS2 nanoscrolls prepared using an ethanol droplet (referred to as MoS2 NS-E) greatly decreased, indicating the loss of encapsulated ethanol in MoS2 NS-E. While the height of MoS2 NS-W was almost unchanged under the same conditions, implying that no water was embedded in the scroll. Compared to the MoS2 NS-E, the MoS2 NS-W shows more ULF breathing mode peaks, confirming the stronger interlayer interaction. In addition, the MoS2 NS-W shows a higher Young's modulus than MoS2 NS-E, which could arise from the closely packed scroll structure. Importantly, the MoS2 NS-W device showed a photosensitivity 1 order of magnitude higher than that of the MoS2 NS-E device under blue, green, and red lasers, respectively. The decreased photosensitivity of MoS2 NS-E was attributed to the larger dark current, which might be assigned to the adsorbed ethanol between the adjacent layers in MoS2 NS-E. Our work provides a solvent-free method to prepare closely packed MoS2 nanoscrolls at large scale and demonstrates their great potential for high-performance optoelectronic devices.

Ordered clustering of single atomic Te vacancies in atomically thin PtTe2 promotes hydrogen evolution catalysis.

Exposing and stabilizing undercoordinated platinum (Pt) sites and therefore optimizing their adsorption to reactive intermediates offers a desirable strategy to develop highly efficient Pt-based electrocatalysts. However, preparation of atomically controllable Pt-based model catalysts to understand the correlation between electronic structure, adsorption energy, and catalytic properties of atomic Pt sites is still challenging. Herein we report the atomically thin two-dimensional PtTe2 nanosheets with well-dispersed single atomic Te vacancies (Te-SAVs) and atomically well-defined undercoordinated Pt sites as a model electrocatalyst. A controlled thermal treatment drives the migration of the Te-SAVs to form thermodynamically stabilized, ordered Te-SAV clusters, which decreases both the density of states of undercoordinated Pt sites around the Fermi level and the interacting orbital volume of Pt sites. As a result, the binding strength of atomically defined Pt active sites to H intermediates is effectively reduced, which renders PtTe2 nanosheets highly active and stable in hydrogen evolution reaction.

Electrochemically Exfoliated Platinum Dichalcogenide Atomic Layers for High-Performance Air-Stable Infrared Photodetectors.

Platinum dichalcogenide (PtX2), an emergent group-10 transition metal dichalcogenide (TMD) has shown great potential in infrared photonic and optoelectronic applications due to its layer-dependent electronic structure with potentially suitable bandgap. However, a scalable synthesis of PtSe2 and PtTe2 atomic layers with controlled thickness still represents a major challenge in this field because of the strong interlayer interactions. Herein, we develop a facile cathodic exfoliation approach for the synthesis of solution-processable high-quality PtSe2 and PtTe2 atomic layers for high-performance infrared (IR) photodetection. As-exfoliated PtSe2 and PtTe2 bilayer exhibit an excellent photoresponsivity of 72 and 1620 mA W-1 at zero gate voltage under a 1540 nm laser illumination, respectively, approximately several orders of magnitude higher than that of the majority of IR photodetectors based on graphene, TMDs, and black phosphorus. In addition, our PtSe2 and PtTe2 bilayer device also shows a decent specific detectivity of beyond 109 Jones with remarkable air-stability (>several months), outperforming the mechanically exfoliated counterparts under the laser illumination with a similar wavelength. Moreover, a high yield of PtSe2 and PtTe2 atomic layers dispersed in solution also allows for a facile fabrication of air-stable wafer-scale IR photodetector. This work demonstrates a new route for the synthesis of solution-processable layered materials with the narrow bandgap for the infrared optoelectronic applications.

Atomically Dispersed Indium Sites for Selective CO2 Electroreduction to Formic Acid.

An atomically dispersed structure is attractive for electrochemically converting carbon dioxide (CO2) to fuels and feedstock due to its unique properties and activity. Most single-atom electrocatalysts are reported to reduce CO2 to carbon monoxide (CO). Herein, we develop atomically dispersed indium (In) on a nitrogen-doped carbon skeleton (In-N-C) as an efficient catalyst to produce formic acid/formate in aqueous media, reaching a turnover frequency as high as 26771 h-1 at -0.99 V relative to a reversible hydrogen electrode (RHE). Electrochemical measurements show that trace amounts of In loaded on the carbon matrix significantly improve the electrocatalytic behavior for the CO2 reduction reaction, outperforming conventional metallic In catalysts. Further experiments and density functional theory (DFT) calculations reveal that the formation of intermediate *OCHO on isolated In sites plays a pivotal role in the efficiency of the CO2-to-formate process, which has a lower energy barrier than that on metallic In.

General, Metal-free Synthesis of Carbon Nanofiber Assemblies from Plant Oils.

We designed a metal-free synthesis of carbon nanofiber based on ketene chemistry using phosphorus pentoxide (P2 O5 ) and vegetable oil. Based on the characterization of intermediates, P2 O5 -oil reaction yielded most possibly alkylketenes, which polymerized into poly(ketene) with abundant enol groups. The enol groups further reacted with P2 O5 , forcing the poly(ketene) to assemble into a nano-sized preassembly structure. Moderate heating transforms these structures into carbonaceaus nanofibers. This approach is applicable to other chemicals with similar structure to vegetable oil. The carbon nanofibers with P-O-C functionalization show relatively high graphitization degree and promising textural properties. The C-O-P environment accounts for 66 at % of the total P and creates a superior thermal stability. As a model application, a CDI system built of a carbon-nanofiber-based electrode countered by an activated carbon-based electrode exhibited exceptional performance.

Atomically-precise dopant-controlled single cluster catalysis for electrochemical nitrogen reduction.

The ability to precisely engineer the doping of sub-nanometer bimetallic clusters offers exciting opportunities for tailoring their catalytic performance with atomic accuracy. However, the fabrication of singly dispersed bimetallic cluster catalysts with atomic-level control of dopants has been a long-standing challenge. Herein, we report a strategy for the controllable synthesis of a precisely doped single cluster catalyst consisting of partially ligand-enveloped Au4Pt2 clusters supported on defective graphene. This creates a bimetal single cluster catalyst (Au4Pt2/G) with exceptional activity for electrochemical nitrogen (N2) reduction. Our mechanistic study reveals that each N2 molecule is activated in the confined region between cluster and graphene. The heteroatom dopant plays an indispensable role in the activation of N2 via an enhanced back donation of electrons to the N2 LUMO. Moreover, besides the heteroatom Pt, the catalytic performance of single cluster catalyst can be further tuned by using Pd in place of Pt as the dopant.

Real-Space Imaging of a Single-Molecule Monoradical Reaction.

Organic radicals consisting of light elements exhibit a low spin-orbit coupling and weak hyperfine interactions with a long spin coherence length, which are crucial for future applications in molecular spintronics. However, the synthesis and characterization of these organic radicals have been a formidable challenge due to their chemical instability arising from unpaired electrons. Here, we report a direct imaging of the surface chemical transformation of an organic monoradical synthesized via the monodehydrogenation of a chemically designed precursor. Bond-resolved scanning tunneling microscopy unambiguously resolves various products formed through a complex structural dissociation and rearrangement of organic monoradicals. Density functional theory calculations reveal detailed reaction pathways from the monoradical to different cyclized products. Our study provides unprecedented insights into complex surface reaction mechanisms of organic radical reactions at the single molecule level, which may guide the design of stable organic radicals for future quantum technology applications.

Deficiency of microRNA-628-5p promotes the progression of gastric cancer by upregulating PIN1.

Gastric cancer is one of the most common cancer and is the second leading cause of cancer-related mortality in the world. PIN1, belonging to peptidyl-prolyl cis-trans isomerase family, uniquely catalyzes the structural transformation of phosphorylated Ser/Thr-Pro motif. It's high expressed in most cancers and promotes their progression. However, the mechanism of PIN1 high expression and its function in gastric cancer progression are still unclear. In this research, we revealed that PIN1 not only promotes the proliferation and colony formation of gastric cancer, but also increases its migration and invasion. The PIN1 expression in metastasis lesion is usually higher than the corresponding primary site. Inhibiting PIN1 by shRNA suppresses the progression of gastric cancer significantly. Besides, we demonstrated that miR-628-5p is a novel PIN1-targeted microRNA, and the expression of miR-628-5p is negatively correlated with PIN1 in gastric cancer. Exogenous expression of miR-628-5p inhibits the progression of gastric cancer that revered by restoring PIN1 expression. However, miR-628-5p is downregulated in majority of gastric cancer tissue especially in metastasis lesion. The lower miR-628-5p level indicates poorer prognosis. In summary, our study demonstrated that deficient miR-628-5p expression facilitates the expression of PIN1, and consequently promotes the progression of gastric cancer.

Effect of Structure and Intramolecular Distances on Photoswitchable Magnetic Resonance Imaging Contrast Agents.

Light-activated sensors are of great interest for biological applications but are limited by the depth of penetration of light. We have been interested in transducing light activation to a magnetic signal that can be detected through noninvasive imaging by magnetic resonance imaging (MRI). We have previously developed agents incorporating spiropyran derivatives as the sensing moiety and characterized features that influence photoswitching; however, we found the MRI response to be unpredictable. In this work, we delve deeper into the potential mechanisms for the observed MRI responses in an effort to better understand the structural effects on controlling magnetic properties. A series of light-activatable MRI contrast agents were synthesized and characterized to assess the effect of spiropyran positioning on contrast agent functions and properties. These compounds are based on the same spiropyran skeleton, also named 1',3',3'-trimethyl-6-nitrospiro[chromene-2,2-indoline], which is linked with an MRI contrast agent, gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7-triacetate (DO3A). We investigated the photo-to-magnetic conversion properties of these novel compounds by adjusting linker lengths over a range from three to seven methylene groups. The primary results indicated that the contrast agent with a five-carbon linker (25) showed the highest light-sensing ability after irradiation with visible light. The results will aid in the design of future spiropyran-based MRI sensors.

EEG dynamical network analysis method reveals the neural signature of visual-motor coordination.

Human visual-motor coordination is an essential function of movement control, which requires interactions of multiple brain regions. Understanding the cortical-motor coordination is important for improving physical therapy for motor disabilities. However, its underlying transient neural dynamics is still largely unknown. In this study, we applied an eigenvector-based dynamical network analysis method to investigate the functional connectivity calculated from electroencephalography (EEG) signals under visual-motor coordination task and to identify its meta-stable states dynamics. We first tested this signal processing on a simulated network to evaluate it in comparison with other dynamical methods, demonstrating that the eigenvector-based dynamical network analysis was able to correctly extract the dynamical features of the evolving networks. Subsequently, the eigenvector-based analysis was applied to EEG data collected under a visual-motor coordination experiment. In the EEG study with participants, the results of both topological analysis and the eigenvector-based dynamical analysis were able to distinguish different experimental conditions of visual tracking task. With the dynamical analysis, we showed that different visual-motor coordination states can be distinguished by investigating the meta-stable states dynamics of the functional connectivity.

CircMRPS35 suppresses gastric cancer progression via recruiting KAT7 to govern histone modification.

BACKGROUND: Aberrant expression of circular RNAs contributes to the initiation and progression of cancers, but the underlying mechanism remains elusive. METHODS: RNA-seq and qRT-PCR were performed to screen differential expressed circRNAs between gastric cancer tissues and adjacent normal tissues. Candidate circRNA (circMRPS35) was screened out and validated by qRT-PCR. Cell proliferation and invasion ability were determined by CCK-8 and cell invasion assays. RNA-seq, GO-pathway, RNA pull-down and ChIRP were further applied to search for detailed mechanism. RESULTS: Here, a novel circRNA named circMRPS35, was screened out by RNA-seq in gastric cancer tissues, whose expression is related to clinicopathological characteristics and prognosis in gastric cancer patients. Biologically, circMRPS35 suppresses the proliferation and invasion of gastric cancer cells in vitro and in vivo. Mechanistically, circMRPS35 acts as a modular scaffold to recruit histone acetyltransferase KAT7 to the promoters of FOXO1 and FOXO3a genes, which elicits acetylation of H4K5 in their promoters. Particularly, circMRPS35 specifically binds to FOXO1/3a promoter regions directly. Thus, it dramatically activates the transcription of FOXO1/3a and triggers subsequent response of their downstream target genes expression, including p21, p27, Twist1 and E-cadherin, resulting in the inhibition of cell proliferation and invasion. Moreover, circMRPS35 expression positively correlates with that of FOXO1/3a in gastric cancer tissues. CONCLUSIONS: Our findings not only reveal the pivotal roles of circMRPS35 in governing histone modification in anticancer treatment, but also advocate for triggering circMRPS35/KAT7/FOXO1/3a pathway to combat gastric cancer.