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A novel antiferroelectric material, PbSnO3 (PSO), was introduced into a resistive random access memory (RRAM) to reveal its resistive switching (RS) properties. It exhibits outstanding electrical performance with a large memory window (>104), narrow switching voltage distribution (±2 V), and low power consumption. Using high-resolution transmission electron microscopy, we observed the antiferroelectric properties and remanent polarization of the PSO thin films. The in-plane shear strains in the monoclinic PSO layer are attributed to oxygen octahedral tilts, resulting in misfit dislocations and grain boundaries at the PSO/SRO interface. Furthermore, the incoherent grain boundaries between the orthorhombic and monoclinic phases are assumed to be the primary paths of Ag+ filaments. Therefore, the RS behavior is primarily dominated by antiferroelectric polarization and defect mechanisms for the PSO structures. The RS behavior of antiferroelectric heterostructures controlled by switching spontaneous polarization and strain, defects, and surface chemistry reactions can facilitate the development of new antiferroelectric device systems.
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Organic Raman probes, including polymers and small molecules, have attracted great attention in biomedical imaging owing to their excellent biocompatibility. However, the development of organic Raman probes is usually hindered by a mismatch between their absorption spectra and wavelength-fixed excitation, which makes it difficult to achieve resonance excitation necessary to obtain strong Raman signals. Herein, we introduce a covalent organic framework (COF) into the fine absorption spectrum regulation of organic Raman probes, resulting in their significant Raman signal enhancement. In representative examples, a polymer poly(diketopyrrolopyrrole-p-phenylenediamine) (DPP-PD) and a small molecule azobenzene are transformed into the corresponding COF-structured Raman probes. Their absorption peaks show an accurate match of less than 5 nm with the NIR excitation. As such, the COF-structured Raman probes acquire highly sensitive bioimaging capabilities compared to their precursors with negligible signals. By further mechanism studies, we discover that the crystallinity and size of COFs directly affect the π-conjugation degree of Raman probes, thus changing their bandgaps and absorption spectra. Our study offers a universal and flexible method for improving the signal performance of organic Raman probes without changing their structural units, making it more convenient to obtain the highly sensitive organic Raman probes for in vivo bioimaging.
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Espectrometría Raman , Espectrometría Raman/métodos , Animales , Humanos , Ratones , Compuestos Azo/química , Estructuras Metalorgánicas/química , Polímeros/química , Estructura Molecular , Fenilendiaminas/químicaRESUMEN
High-entropy oxides (HEOs) are promising anode materials for lithium-ion batteries (LIBs), owing to their stable crystal structure, superionic conductivity, and high capacity. In this study, the (Cr, Mn, Fe, Co, and Ni)3O4 HEO via solid-state reaction is prepared. To improve the synthetic efficiency, it is necessary to understand the formation mechanism. Therefore, a high-resolution transmission electron microscopy (HRTEM) is used to record information during calcination at increasing temperature. The overall formation process included MnO2 and NiO aggregation at 500 °C, followed by (Mn, and Ni)3O4 combined with Co3O4 at 600 °C to form (Mn, Co, and Ni)3O4. At higher temperatures, Fe2O3 and Cr2O3 sequentially combined with (Mn, Co, and Ni)3O4 and formed the (Cr, Mn, Fe, Co, Ni)3O4 at 900 °C. In addition, the valence-state-changing mechanisms and ion arrangements of (Cr, Mn, Fe, Co, and Ni)3O4 are determined using electron energy loss spectroscopy (EELS) and extended X-ray absorption fine structure (EXAFS). This study successfully revealed the formation of HEO at atomic scale. The results provide valuable insights for improving the manufacturing process of (Cr, Mn, Fe, Co, and Ni)3O4 HEOs, which is expected to play a vital role in the development of anode materials for next-generation LIBs.
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BACKGROUND: Microbial communities are of critical importance in the human host. The lung and gut microbial communities represent the most essential microbiota within the human body, collectively referred to as the gut-lung axis. However, the differentiation between these communities and their influence on clinical outcomes in critically ill patients remains uncertain. METHODS: An observational cohort study was obtained in the intensive care unit (ICU) of an affiliated university hospital. Sequential samples were procured from two distinct anatomical sites, namely the respiratory and intestinal tracts, at two precisely defined time intervals: within 48 h and on day 7 following intubation. Subsequently, these samples underwent a comprehensive analysis to characterize microbial communities using 16S ribosomal RNA (rRNA) gene sequencing and to quantify concentrations of fecal short-chain fatty acids (SCFAs). The primary predictors in this investigation included lung and gut microbial diversity, along with indicator species. The primary outcome of interest was the survival status at 28 days following mechanical ventilation. RESULTS: Sixty-two mechanically ventilated critically ill patients were included in this study. Compared to the survivors, the diversity of microorganisms was significantly lower in the deceased, with a significant contribution from the gut-originated fraction of lung microorganisms. Lower concentrations of fecal SCFAs were detected in the deceased. Multivariate Cox regression analysis revealed that not only lung microbial diversity but also the abundance of Enterococcaceae from the gut were correlated with day 28 mortality. CONCLUSION: Critically ill patients exhibited lung and gut microbial dysbiosis after mechanical ventilation, as evidenced by a significant decrease in lung microbial diversity and the proliferation of Enterococcaceae in the gut. Levels of fecal SCFAs in the deceased served as a marker of imbalance between commensal and pathogenic flora in the gut. These findings emphasize the clinical significance of microbial profiling in predicting the prognosis of ICU patients.
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Microbioma Gastrointestinal , Microbiota , Humanos , Enfermedad Crítica , Respiración Artificial , Microbioma Gastrointestinal/genética , ARN Ribosómico 16S/genética , Microbiota/genética , Pulmón , Heces , Ácidos Grasos VolátilesRESUMEN
INTRODUCTION: The potential association between severe postoperative complications (SPC) and the oncological outcomes of esophageal squamous cell carcinoma (ESCC) patients according to the different Naples Prognostic Score (NPS) of the inflammatory nutritional status after minimally invasive esophagectomy (MIE) is unclear. METHODS: Kaplan-Meier survival analysis was used to evaluate overall survival (OS) and disease-free survival (DFS) between with or without SPC (Clavien-Dindo grade ≥ III) in low NPS status (NPS = 0 or 1) and high NPS status (NPS = 2 or 3 or 4) patients. Cox multivariable analysis was carried out to analyze the various independent factors of OS and DFS, and a nomogram based on SPC was established. RESULTS: A total of 20.7% (125/604) ESCC patients developed SPC after MIE. Patients with SPC exhibited poor 5-year OS and DFS compared to those without SPC (all P < 0.001). Further analysis revealed that SPC significantly reduced OS and DFS in patients with high NPS status (all P < 0.001) but had little effect on the prognosis of patients with low NPS status (all P > 0.05). Multivariable Cox analysis revealed that SPC could be an independent influence indicator for OS and DFS in patients with high NPS status. Therefore, a novel nomogram combining SPC and tumor-node-metastasis (TNM) staging has been developed, which was found to be relatively more accurate in predicting OS and DFS than TNM staging alone. CONCLUSION: Severe complications can adversely affect the long-term oncological outcome of ESCC patients with high systemic inflammatory response and malnutrition after MIE.
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Neoplasias Esofágicas , Carcinoma de Células Escamosas de Esófago , Humanos , Carcinoma de Células Escamosas de Esófago/cirugía , Neoplasias Esofágicas/patología , Estado Nutricional , Esofagectomía/efectos adversos , Pronóstico , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/etiología , Estudios RetrospectivosRESUMEN
The intraoperative imaging applications of a large number of Raman probes are hampered by the overlap of their signals with the background Raman signals generated by biological tissues. Here, we describe a molecular planarization strategy for adjusting the Raman shift of these Raman probes to avoid interference. Using this strategy, we modify the backbone of thiophene polymer-poly(3-hexylthiophene) (P3HT), and obtain the adjacent thiophene units planarized polycyclopenta[2,1-b;3,4-b']dithiophene (PCPDT). Compared with P3HT whose signal is disturbed by the Raman signal of lipids in tissues, PCPDT exhibits a 60 cm-1 blueshift in its characteristic signal. Therefore, the PCPDT probe successfully avoids the signal of lipids, and achieves intraoperative imaging of lymph nodes and tumor micrometastasis as small as 0.30 × 0.36 mm. In summary, our study presents a concise molecular planarization strategy for regulating the signal shift of Raman probes, and brings a tunable thiophene polymer probe for high-precision intraoperative Raman imaging.
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Micrometástasis de Neoplasia , Espectrometría Raman , Humanos , Espectrometría Raman/métodos , Ganglios Linfáticos/diagnóstico por imagen , Ganglios Linfáticos/cirugía , Polímeros/química , Tiofenos , LípidosRESUMEN
Surface diffusion is intimately correlated with crystal orientation and surface structure. Fast surface diffusion accelerates phase transformation and structural evolution of materials. Here, through in situ transmission electron microscopy observation, we show that a copper nanowire with dense nanoscale coherent twin-boundary (CTB) defects evolves into a zigzag configuration under electric-current driven surface diffusion. The hindrance at the CTB-intercepted concave triple junctions decreases the effective surface diffusivity by almost 1 order of magnitude. The energy barriers for atomic migration at the concave junctions and different faceted surfaces are computed using density functional theory. We proposed that such a stable zigzag surface is shaped not only by the high-diffusivity facets but also by the stalled atomic diffusion at the concave junctions. This finding provides a defect-engineering route to develop robust interconnect materials against electromigration-induced failures for nanoelectronic devices.
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In this study, facile salt-assisted chemical vapor deposition (CVD) was used to synthesize ultrathin non-van der Waals chromium sulfide (Cr2S3) with a thickness of â¼1.9 nm. The structural transformation of as-grown Cr2S3 was studied using advanced in situ heating techniques combined with transmission electron microscopy (TEM). Two-dimensional (2D) and quasi-one-dimensional (1D) samples were fabricated to investigate the connection between specific planes and the dynamic behavior of the structural variation. The rearrangement of atoms during the phase transition was driven by the loss of sulfur atoms at elevated temperatures, resulting in increased free energy. A decrease in the ratio of the (001) plane led to an overall increase in surface energy, thus lowering the critical phase transition temperature. Our study provides detailed insight into the mechanism of structural transformation and the critical factors governing transition temperature, thus paving the way for future studies on intriguing Cr-S compounds.
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Raman imaging is a powerful tool for the diagnosis of cancers and visualization of various biological processes. Polymers possessing excellent biocompatibility are promising probes for Raman imaging. However, few polymers are reported to serve as Raman probes for in vivo imaging, mainly due to the intrinsic weak Raman signal intensity and fluorescence interference of these polymers. Herein, a poly(indacenodithiophene-benzothiadiazole) (IDT-BT) polymer is presented, which emits unprecedentedly strong Raman signals under the near-infrared wavelength (785 nm) excitation, thus functioning as a Raman probe for ultrasensitive in vivo Raman imaging. Further mechanistic studies unveil that the unique Raman feature of the IDT-BT polymer relies on molecularly regulating its absorbance edge adjacent to the desired excitation wavelength, thus avoiding fluorescence interference and simultaneously emitting strong Raman scattering under preresonant excitation. Taking advantage of this discipline, the IDT-BT polymeric probe successfully realizes intraoperative Raman imaging of micrometastasis as small as 0.3 mm × 0.3 mm, comparable to the most sensitive Raman probes currently reported. Impressively, the IDT-BT enables noninvasive microvascular imaging, which is not achieved using other Raman probes. This work opens a new avenue toward the development of polymeric Raman probes for in vivo Raman imaging.
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Diagnóstico por Imagen , Neoplasias , Humanos , Neoplasias/diagnóstico por imagen , Polímeros , Espectrometría Raman/métodosRESUMEN
2D materials have great potential for not only device scaling but also various applications. To prompt the development of 2D electronics and optoelectronics, a better understanding of the limitation of materials is essential. Material failure caused by bias can lead to variations in device behavior and even electrical breakdown. In this study, the structural evolution of monolayer MoS2 with high bias is revealed via in situ transmission electron microscopy at the atomic scale. The biasing process is recorded and studied with the aid of aberration-corrected scanning transmission electron microscopy. The effects of electron beam irradiation and biasing are also discussed through the combination of experiments and theory. It is found that the Mo nanoclusters result from disintegration of MoS2 and sulfur depletion, which are induced by Joule heating. The thermal stress can also damage the MoS2 layer and form long cracks in both in situ and ex situ biasing cases. Investigation of the results obtained with different applied voltages helps to further verify the mechanism of evolution and provide a comprehensive study of the function of biasing.
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Recently, perovskite (PV) oxides with ABO3 structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeOx is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO2.5 is grown on an Nb-STO conductive substrate epitaxially. CaFeOx exhibits excellent endurance and reliability. In addition, the CaFeOx also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeOx . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeOx after the switching behavior. This study not only reveals the switching mechanism of CaFeOx , but also provides a PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.
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In order to develop multi-residues rapid detection, the bispecific aptamers against malachite green (MG) and leucomalachite green (LMG) were isolated by the capture systematic evolution of ligands by exponential enrichment (Capture-SELEX). After thirteen rounds of selection, the enriched ssDNA pools were sent for high-throughput sequencing. Nine aptamer candidates (A1-A9) were picked out to test their specificity by gold nanoparticles (AuNPs) colorimetric assay. Three aptamers (A2, A3, A5) with good selectivity were truncated to verify their affinity by fluorescence assay. Finally, three truncated aptamers (A2-a, A3-a, A5-a) with bispecificity and high affinity were identified. For LMG, the dissociation constant (Kd) of them were 8.4 ± 0.8 nM, 8.2 ± 1.2 nM, and 13.7 ± 1.4 nM, respectively. For MG, Kd of them were 3.4 ± 0.3 µM, 2.3 ± 0.2 µM, 3.0 ± 0.2 µM. Among them, A3-a is the best. Our work will provide novel probes for the development of multi-residues rapid detection as well as opportunities for multiple target aptamer discovery.
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Aptámeros de Nucleótidos , Nanopartículas del Metal , Técnica SELEX de Producción de Aptámeros , Oro/química , Aptámeros de Nucleótidos/química , Nanopartículas del Metal/químicaRESUMEN
INTRODUCTION: Left ventricular diastolic dysfunction (LVDD) adversely impacts renal function, and E/e' is a significant predictor of adverse kidney events under different clinical conditions. However, no studies have evaluated the association between LVDD and septic acute kidney injury (AKI) among patients with severe sepsis and septic shock. METHODS: This multicenter retrospective study evaluated adult patients with severe sepsis or septic shock between January 1, 2013, and December 31, 2019, who underwent echocardiography within 24 hours after admission to an intensive care unit. RESULTS: A total of 495 adult patients were enrolled in the study. LVDD grades II and III were associated with severe (stage 3) AKI (p < 0.001, p for trend < 0.001). E/e' and e' were risk factors for septic AKI (OR, 1.155; 95% CI, 1.088-1.226, p < 0.001; and OR, 7.218; 95% CI, 2.942-17.712, p < 0.001, respectively) in the multivariate logistic regression analysis. The area under the receiver operating characteristic curve of E/e' and e' was 0.728 (95% CI, 0.680-0.777, p < 0.001) and 0.715 (95% CI, 0.665-0.764, p < 0.001), respectively. CONCLUSIONS: LVDD was associated with septic AKI, and E/e' and e' are useful predictors of septic AKI among patients with severe sepsis or septic shock. TRIAL REGISTRATION: The study was registered at the Chinese Clinical Trial Registry (Protocol No. ChiCTR2000033083).
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Lesión Renal Aguda , Sepsis , Choque Séptico , Disfunción Ventricular Izquierda , Lesión Renal Aguda/complicaciones , Adulto , Humanos , Estudios Retrospectivos , Sepsis/complicaciones , Choque Séptico/complicaciones , Disfunción Ventricular Izquierda/complicacionesRESUMEN
Crystalline Mo5O14 exhibits distinctive structural features such as tunnel structure and pseudolamellar arrangement according to the ideal model. However, the spatial resolution of the conventional technique of transmission electron microscopy (TEM) is insufficient to distinguish the actual positions of atoms. In this work, we aimed to systematically analyze and identify the Mo5O14 nanowires fabricated by the chemical vapor deposition (CVD) process. Utilizing high-angle annular dark-field (HAADF), annular bright-field (ABF), and enhanced annular bright-field (E-ABF) within the scanning transmission electron microscope (STEM) mode reveals the structural features at the atomic scale. In addition, the ultrahigh resolution images have confirmed the crystallographic insights in [001] growth direction for the Mo5O14 nanowires with a tunnel structure throughout the nanowire. The cross-sectional images show the unique close-packed plane and atomic arrangement with a network of MoO6 octahedra and MoO7 pentagonal bipyramids. These results are consistent with the theoretical atomic arrangement, supporting the realization of Mo5O14-type catalysts used in the selective oxidation process and battery applications.
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Layered MoS2 is a prospective candidate for use in energy harvesting, valleytronics, and nanoelectronics. Its properties strongly related to its stacking configuration and the number of layers. Due to its atomically thin nature, understanding the atomic-level and structural modifications of 2D transition metal dichalcogenides is still underdeveloped, particularly the spatial control and selective precision. Therefore, the development of nanofabrication techniques is essential. Here, an atomic-scale approach used to sculpt 2D few-layer MoS2 into lateral heterojunctions via in situ scanning/transmission electron microscopy (STEM/TEM) is developed. The dynamic evolution is tracked using ultrafast and high-resolution filming equipment. The assembly behaviors inherent to few-layer 2D-materials are observed during the process and included the following: scrolling, folding, etching, and restructuring. Atomic resolution STEM is employed to identify the layer variation and stacking sequence for this new 2D-architecture. Subsequent energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy analyses are performed to corroborate the elemental distribution. This sculpting technique that is established allows for the formation of sub-10 nm features, produces diverse nanostructures, and preserves the crystallinity of the material. The lateral heterointerfaces created in this study also pave the way for the design of quantum-relevant geometries, flexible optoelectronics, and energy storage devices.
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A graphene oxide/poly(N-isopropylacrylamide-co-ß-cyclodextrin) (GO/poly(NIPAM-co-ß-CD)) hydrogel has been synthesized through host-guest interaction between ß-cyclodextrin (ß-CD) and the isopropyl group of N-isopropylacrylamide (NIPAM). The product exhibits rapid responses to the stimuli of temperature and near-infrared (NIR) irradiation, self-healing properties, and excellent mechanical properties. The host-guest interaction serves as the main physical cross-linker, while a hydrogen bond between the hydroxyl group of ß-CD, GO sheets and amide group of NIPAM acts as a secondary cross-linker. The volume phase transition temperature and NIR response rate of such a hydrogel are controlled by its contents of ß-CD and GO. The obtained hydrogels showing excellent properties might be applied in remote contactless control devices in advanced smart technologies. Based on the excellent characteristics of the hydrogels, remote light-controlled switches have been designed, and more applications will be explored, such as intelligent light-controlled drivers and soft robots.
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Metal oxides have attracted substantial attention over the years and are commonly used in the semiconductor industry because of their excellent physical and chemical properties. Among the various metal oxides, cuprous oxide (Cu2O) is regarded as a promising material. It is inexpensive, earth-abundant, and nontoxic; therefore, it can be used in catalysis, sensors, solar cells, and p-type semiconductors. However, the redox reaction of Cu2O is still uncertain. The size, morphology, and structure of Cu2O strongly influence its properties. In this work, we developed a new synthesis method of Cu2O that involves reducing the precursor by an electron beam without reducing agent. The growth process of Cu2O nanocubes was observed via in situ liquid cell transmission electron microscopy (in situ LCTEM). The nucleation kinetics, oscillating growth behavior, and redox reaction of the Cu2O nanocubes in the liquid phase were systematically studied. Cu2O exhibited a round shape at the beginning and transformed into a cubic shape afterward. Interestingly, the Cu2O nanocubes grew clearly under long-term observation; however, their diameters increased and fluctuated during the short-term observation. The electron beam not only stimulated the solution to reduce the nanocubes but also caused electron radiation effect to the nanocubes. During the Cu2O growth and dissolution, the cubic shape evolved with specific planes in the {100} family. Our direct observation sheds light on the preparation of Cu2O by a reduction method, extending the study of reaction kinetics and providing a new way to synthesize metal oxides.
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Electrical contacts often dominate charge transport properties at the nanoscale because of considerable differences in nanoelectronic device interfaces arising from unique geometric and electrostatic features. Transistors with a tunable Schottky barrier between the metal and semiconductor interface might simplify circuit design. Here, germanium nanowire (Ge NW) transistors with Cu3 Ge as source/drain contacts formed by both buffered oxide etching treatments and rapid thermal annealing are reported. The transistors based on this Cu3 Ge/Ge/Cu3 Ge heterostructure show ambipolar transistor behavior with a large on/off current ratio of more than 105 and 103 for the hole and electron regimes at room temperature, respectively. Investigations of temperature-dependent transport properties and low-frequency current fluctuations reveal that the tunable effective Schottky barriers of the Ge NW transistors accounted for the ambipolar behaviors. It is further shown that this ambipolarity can be used to realize binary-signal and data-storage functions, which greatly simplify circuit design compared with conventional technologies.
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Transition metal oxide nanowires have attracted extensive attention because of their physical characteristics. Among them, ZnO nanowires have great potential. Due to the multifunctional properties of ZnO, devices built using ZnO-based heterostructures always perform well. In this study, interesting diffusion behavior between ZnO nanowires and Fe metal was observed by using in situ transmission electron microscopy. ZnO nanowires and Fe metal were annealed under ultrahigh vacuum (UHV) conditions at 800 K. By controlling the annealing time for the solid-state diffusion, porous Fe3O4 and unique ZnO/porous Fe3O4 nanowire heterostructures were formed. As-formed porous Fe3O4 nanowires with voids can be divided into two types by appearance: plate-like voids and zigzag-like hollow voids. From high-resolution transmission electron microscopy (HRTEM) images and fast Fourier transform (FFT) diffraction patterns, we found that plate-like voids formed along the {111} plane, which was the close-packed plane of Fe3O4, and that zigzag-like hollow voids formed along the {111}/{022} planes. Moreover, a transition region existed during diffusion, with a parallel relationship found between the Fe3O4 crystal with plate-like voids and the ZnO crystal. A sharp interface was determined to exist between the Fe3O4 crystal with zigzag-like hollow voids and ZnO. These oriented porous Fe3O4/ZnO axial nanowire heterostructures exhibited a unique appearance and interesting formation behavior. Furthermore, the structures had a high surface-area-to-volume ratio, which is promising for sensing applications.
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The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) nanowires, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu nanowire growth has been found to be important. Here, we report the synthesis of defect-free single-crystalline Cu nanowires by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop of an amorphous carbon (a-C) lacey film surface. Without a metal-catalyst or induced defects, the high quality Cu nanowires formed with high aspect ratio and high growth rate of 578 nm/s. The dynamic study of the growth of heterogeneous nanowires was conducted in situ with a high-resolution transmission electron microscope. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu nanowire on a-C lacey film.