Atomic dynamics of electrified solid-liquid interfaces in liquid-cell TEM.

Electrified solid-liquid interfaces (ESLIs) play a key role in various electrochemical processes relevant to energy1-5, biology6 and geochemistry7. The electron and mass transport at the electrified interfaces may result in structural modifications that markedly influence the reaction pathways. For example, electrocatalyst surface restructuring during reactions can substantially affect the catalysis mechanisms and reaction products1-3. Despite its importance, direct probing the atomic dynamics of solid-liquid interfaces under electric biasing is challenging owing to the nature of being buried in liquid electrolytes and the limited spatial resolution of current techniques for in situ imaging through liquids. Here, with our development of advanced polymer electrochemical liquid cells for transmission electron microscopy (TEM), we are able to directly monitor the atomic dynamics of ESLIs during copper (Cu)-catalysed CO2 electroreduction reactions (CO2ERs). Our observation reveals a fluctuating liquid-like amorphous interphase. It undergoes reversible crystalline-amorphous structural transformations and flows along the electrified Cu surface, thus mediating the crystalline Cu surface restructuring and mass loss through the interphase layer. The combination of real-time observation and theoretical calculations unveils an amorphization-mediated restructuring mechanism resulting from charge-activated surface reactions with the electrolyte. Our results open many opportunities to explore the atomic dynamics and its impact in broad systems involving ESLIs by taking advantage of the in situ imaging capability.

Hydraulic-driven adaptable morphing active-cooling elastomer with bioinspired bicontinuous phases.

The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation.

Unveiling Corrosion Pathways of Sn Nanocrystals through High-Resolution Liquid Cell Electron Microscopy.

Unveiling materials' corrosion pathways is significant for understanding the corrosion mechanisms and designing corrosion-resistant materials. Here, we investigate the corrosion behavior of Sn@Ni3Sn4 and Sn nanocrystals in an aqueous solution in real time by using high-resolution liquid cell transmission electron microscopy. Our direct observation reveals an unprecedented level of detail on the corrosion of Sn metal with/without a coating of Ni3Sn4 at the nanometric and atomic levels. The Sn@Ni3Sn4 nanocrystals exhibit "pitting corrosion", which is initiated at the defect sites in the Ni3Sn4 protective layer. The early stage isotropic etching transforms into facet-dependent etching, resulting in a cavity terminated with low-index facets. The Sn nanocrystals under fast etching kinetics show uniform corrosion, and smooth surfaces are obtained. Sn nanocrystals show "creeping-like" etching behavior and rough surfaces. This study provides critical insights into the impacts of coating, defects, and ion diffusion on corrosion kinetics and the resulting morphologies.

Visualizing Facets Asymmetry Induced Directional Movement of Cadmium Chloride Nanomotor.

Nanomotors in solution have many potential applications. However, it has been a significant challenge to realize the directional motion of nanomotors. Here, we report cadmium chloride tetrahydrate (CdCl2·4H2O) nanomotors with remarkable directional movement under electron beam irradiation. Using in situ liquid phase transmission electron microscopy, we show that the CdCl2·4H2O nanoparticle with asymmetric surface facets moves through the liquid with the flat end in the direction of motion. As the nanomotor morphology changes, the speed of movement also changes. Finite element simulation of the electric field and fluid velocity distribution around the nanomotor assists the understanding of ionic self-diffusiophoresis as a driving force for the nanomotor movement; the nanomotor generates its own local ion concentration gradient due to different chemical reactivities on different facets.

TNFR2 promotes pancreatic cancer proliferation, migration, and invasion via the NF-κB signaling pathway.

PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignant disease with low overall survival; chemotherapy and immunotherapy have limited efficacy. Tumor necrosis factor receptor 2 (TNFR2), a type II transmembrane protein, contributes to the development and progression of several tumors. In this study, we elucidated the effect and molecular mechanisms of TNFR2. METHOD: We used The Cancer Genome Atlas and the Genotype-Tissue Expression database to compare the expression of the TNFR2 gene between normal and malignant pancreatic tissue. Using immunohistochemical staining, we divided the patients into high and low-expression groups, then investigated clinicopathologic data and survival curves of pancreatic cancer patients. We measured TNFR2 protein expression in PANC-1 and ASPC-1 pancreatic cancer cells subjected to TNFR2 small interfering RNA or negative control treatment. We performed proliferation, invasion, and migration assays to study the biological effects of TNFR2 in PDAC. The molecular mechanisms were validated using western blotting. RESULTS: TNFR2 was more highly expressed in PDAC cells and tissues than controls. Abundant expression of TNFR2 was associated with aggressive clinicopathologic characteristics and poor outcomes. Overexpression of TNFR2 promoted PDAC cell proliferation, migration, and invasion in vitro. Mechanistically, TNFR2 binds to TNF-α and activates the NF-κB signaling pathway. CONCLUSION: TNFR2 is a prognostic marker that facilitates the proliferation, migration, and invasion of PDAC via the NF-κB signaling pathway. TNFR2 may become a therapeutic target.

Application value and safety of NIPPV combined with routine clearance in the treatment of stroke-associated pneumonia in elderly patients.

OBJECTIVE: To investigate the application value and safety of NIPPV (noninvasive positive pressure ventilation) combined with routine clearance in elderly patients with stroke-associated pneumonia (SAP). METHODS: Altogether 88 elderly SAP patients treated in our hospital from January 2021 to January 2022 were retrospectively evaluated. Among them, 48 cases treated with NIPPV and routine clearance were regarded as an experimental group (EG), and 40 with routine clearance alone were enrolled to a control group (CG). The sputum clearance rate and CPIS score were compared. The safety of NIPPV was evaluated. The clearance treatment cost, hospitalization time and expenses, and the changes of inflammatory factors (IL-6, TNF-α, C-reactive protein (CRP)) were compared before and after treatment. The efficacy of airway clearance after treatment and the risk factors affecting the severity of infection was assessed. RESULTS: The sputum clearance rate in the EG was higher than that in the CG (P < 0.05). After treatment, the CPIS score of EG was lower (P < 0.05). The hospitalization time and expenses of CG were higher. After treatment, the serum inflammatory factors in CG were higher (P < 0.05), while the clinical efficacy of EG was higher (P < 0.05). Treatment plan, course of disease and diabetes are risk factors for postoperative infection. CONCLUSION: NIPPV combined with routine clearance is effective for elderly SAP patients, which can shorten the hospitalization time and reduce the expenses.

Swap motion-directed twinning of nanocrystals.

Twinning frequently occurs in nanocrystals during various thermal, chemical, or mechanical processes. However, the nucleation and propagation mechanisms of twinning in nanocrystals remain poorly understood. Through in situ atomic resolution transmission electron microscopy observation at millisecond temporal resolution, we show the twinning in Pb individual nanocrystals via a double-layer swap motion where two adjacent atomic layers shift relative to one another. The swap motion results in twin nucleation, and it also serves as a basic unit of movement for twin propagation. Our calculations reveal that the swap motion is a phonon eigenmode of the face-centered cubic crystal structure of Pb, and it is enhanced by the quantum size effect of nanocrystals.

Observation of formation and local structures of metal-organic layers via complementary electron microscopy techniques.

Metal-organic layers (MOLs) are highly attractive for application in catalysis, separation, sensing and biomedicine, owing to their tunable framework structure. However, it is challenging to obtain comprehensive information about the formation and local structures of MOLs using standard electron microscopy methods due to serious damage under electron beam irradiation. Here, we investigate the growth processes and local structures of MOLs utilizing a combination of liquid-phase transmission electron microscopy, cryogenic electron microscopy and electron ptychography. Our results show a multistep formation process, where precursor clusters first form in solution, then they are complexed with ligands to form non-crystalline solids, followed by the arrangement of the cluster-ligand complex into crystalline sheets, with additional possible growth by the addition of clusters to surface edges. Moreover, high-resolution imaging allows us to identify missing clusters, dislocations, loop and flat surface terminations and ligand connectors in the MOLs. Our observations provide insights into controllable MOL crystal morphology, defect engineering, and surface modification, thus assisting novel MOL design and synthesis.

Electron Tomography Reveals Porosity Degradation Spatially on Individual Pt-Based Nanocatalysts.

Probing porosity evolution is essential to understand the degradation mechanism of electrocatalytic activity. However, spatially dependent degradation pathways for porous catalysts remain elusive. Here, we reveal the multiple degradation behaviors of individual PtCu3 nanocatalysts spatially by three-dimensional (3D) electron tomography. We demonstrate that the surface area-volume ratio (SVR) of cycled porous particles decreases linearly rather than reciprocally with particle size. Additionally, an improved SVR (about 3-fold enhancement) results in increased oxygen reduction reaction (ORR) efficiency at the early stage. However, in the subsequent cycles, the degradation of catalytic activity is due to the excessive growth of pores, the reduction of reaction sites, and the chemical segregation of Cu atoms. The spatial porosity evolution model of nanocatalysts is applicable for a wide range of catalytic reactions, providing a critical insight into the degradation of catalyst activity.

Solid-liquid-gas reaction accelerated by gas molecule tunnelling-like effect.

Solid-liquid-gas reactions are ubiquitous and are encountered in both nature and industrial processes1-4. A comprehensive description of gas transport in liquid and following reactions at the solid-liquid-gas interface, which is substantial in regard to achieving enhanced triple-phase reactions, remains unavailable. Here, we report a real-time observation of the accelerated etching of gold nanorods with oxygen nanobubbles in aqueous hydrobromic acid using liquid-cell transmission electron microscopy. Our observations reveal that when an oxygen nanobubble is close to a nanorod below the critical distance (~1 nm), the local etching rate is significantly enhanced by over one order of magnitude. Molecular dynamics simulation results show that the strong attractive van der Waals interaction between the gold nanorod and oxygen molecules facilitates the transport of oxygen through the thin liquid layer to the gold surface and thus plays a crucial role in increasing the etching rate. This result sheds light on the rational design of solid-liquid-gas reactions for enhanced activities.

Defect-mediated ripening of core-shell nanostructures.

Understanding nanostructure ripening mechanisms is desirable for gaining insight on the growth and potential applications of nanoscale materials. However, the atomic pathways of nanostructure ripening in solution have rarely been observed directly. Here, we report defect-mediated ripening of Cd-CdCl2 core-shell nanoparticles (CSN) revealed by in-situ atomic resolution imaging with liquid cell transmission electron microscopy. We find that ripening is initiated by dissolution of the nanoparticle with an incomplete CdCl2 shell, and that the areas of the Cd core that are exposed to the solution are etched first. The growth of the other nanoparticles is achieved by generating crack defects in the shell, followed by ion diffusion through the cracks. Subsequent healing of crack defects leads to a highly crystalline CSN. The formation and annihilation of crack defects in the CdCl2 shell, accompanied by disordering and crystallization of the shell structure, mediate the ripening of Cd-CdCl2 CSN in the solution.

Effect of high quality nursing and respiratory training on pulmonary function and quality of life in patients with chronic obstructive pulmonary disease.

OBJECTIVE: This research was aimed to evaluate the impact of high-quality nursing (HQN) plus respiratory training on treatment compliance, pulmonary function (PF) and quality of life (QoL) of patients with chronic obstructive pulmonary disease (COPD). METHODS: We retrospectively analyzed 89 COPD patients who were treated at the affiliated Nanhua Hospital from February 2019 to February 2021. Among them, 40 cases received drug treatment and breathing training as the control group, and 49 cases were supplemented with HQN as the experimental group on the basis of the control group. The changes in PF, quality of life and compliance were compared between the two groups. RESULTS: Vital capacity (VC) and alveolar ventilation (VA) increased in both cohorts after treatment (P < 0.05), and increased more significantly in experimental group compared with control group (P < 0.05). Experimental group also presented markedly higher total effective rate and noticeably lower scores of symptoms, activities and disease impact on daily life than control group (P < 0.05). CONCLUSIONS: HQN plus respiratory training can effectively improve the PF, efficacy and QoL of patients with COPD.

Influence of sub-zero temperature on nucleation and growth of copper nanoparticles in electrochemical reactions.

Cu metal nanostructures have attracted wide interest of study as catalysts for CO2 reduction reaction and other applications. Controlling the structure and morphology of Cu nanostructures during synthesis is crucial for achieving desired properties. Here, we studied temperature effects on electrochemical deposition of Cu nanoparticles. We found the size, nucleation density, and crystallinity of Cu nanoparticles are strongly influenced by low temperature processing. The electrodeposition at low temperature (-20°C) results in clusters of assembled small Cu nanoparticles, which is distinctly different from the large individual highly crystalline Cu nanoparticles obtained from the room temperature process. The differences in Cu nanoparticle morphology and crystallinity are attributed to the variations in reduction reaction rate and surface diffusion. The limitation of the reaction rate promotes multiple nuclei, and low surface diffusion induces poor crystallinity. This study deepens our understanding of low-temperature effects on electrochemical processes assisting the design of diverse hierarchical catalytic materials.

Tailoring atomic 1T phase CrTe2forin situfabrication.

Controllable tailoring and understanding the phase-structure relationship of the 1T phase two-dimensional (2D) materials are critical for their applications in nanodevices. Thein situtransmission electron microscope (TEM) could regulate and monitor the evolution process of the nanostructure of 2D material with atomic resolution. In this work, a controllably tailoring 1T-CrTe2nanopore is carried out by thein situTEM. A preferred formation of the 1T-CrTe2border structure and nanopore healing process are studied at the atomic scale. The controllable tailoring of the 1T phase nanopore could be achieved by regulating the transformation of two types of low indices of crystal faces {101¯0} and {112¯0} at the nanopore border. Machine learning is applied to automatically process the TEM images with high efficiency. By adopting the deep-learning-based image segmentation method and augmenting the TEM images specifically, the nanopore of the TEM image could be automatically identified and the evaluation result of DICE metric reaches 93.17% on test set. This work presents the unique structure evolution of 1T phase 2D material and the computer aided high efficiency TEM data analysis based on deep learning. The techniques applied in this work could be generalized to other materials for controlled nanostructure regulation and automatic TEM image analyzation.

Observation of Surface Ligands-Controlled Etching of Palladium Nanocrystals.

Selective adsorption of ligands on nanocrystal surfaces can affect oxidative etching. Here, we report the etching of palladium nanocrystals imaged using liquid cell transmission electron microscopy. The adsorption of surface ligands (i.e., iron acetylacetonate and its derivatives) and their role as inhibitor molecules on the etching process were investigated. Our observations revealed that the etching was dominated by the interplay between palladium facets and ligands and that the etching exhibited different pathways at different concentrations of ligands. At a low concentration of iron acetylacetonate (0.1 mM), rapid etching primarily at {100} facets led to a concave structure. At a high concentration (1.0 mM), the etch rate was decreased owing to a protective film of iron acetylacetonate on the {100} facets and a round nanoparticle was achieved. Ab initio calculations showed that the differences in adsorption energy of inhibitor molecules on palladium facets were responsible for the etching behavior.

Sub-4 nm Nanodiamonds from Graphene-Oxide and Nitrated Polycyclic Aromatic Hydrocarbons at 423 K.

Nanodiamonds are interesting materials from the point of view of their biocompatibility and their chemical, spectroscopic, and mechanical properties. Current synthetic methods for nanodiamonds involve harsh environments, which are potentially hazardous in addition to being expensive. We report a low-temperature (423 K) hydrothermal approach to form nanodiamonds by using graphene-oxide or nitrated polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, or pyrene) as a starting material. The reaction products contain single-crystalline or twinned nanodiamonds with average diameters in the 2-3 nm range. Theoretical calculations prove that, at the nanoscale, sub-4 nm nanodiamonds may adopt a structure that is more stable than graphene-oxide and nitrated polycyclic aromatic hydrocarbons. Our findings show that sp2 carbon in the polycyclic aromatic precursor can be converted to sp3 carbon under unexpectedly moderate temperature conditions by using nanoscale precursors and thus offer a low-temperature approach for the synthesis of sub-4 nm nanodiamonds.

Development and validation of a novel nomogram for pretreatment prediction of liver metastasis in pancreatic cancer.

PURPOSE: The diagnostic value of nomogram in pancreatic cancer (PC) with liver metastasis (PCLM) is still largely unknown. We sought to develop and validate a novel nomogram for the prediction of liver metastasis in patients with PC. METHOD: About 604 pathologically confirmed PC patients from the Sun Yat-sen University Cancer Center (SYSUCC) between July, 2001 and December, 2013 were retrospectively studied. The SYSUCC cohort was randomly assigned to as the training set and internal validation set. Using these two sets, we derived and validated a prognostic model by using concordance index and calibration curves. Another two independent cohorts between August, 2002 and December, 2013 from the Sun Yat-sen Memorial Hospital (SYSMH, n = 335) and Guangdong General Hospital (GDGH, n = 503) was used for external validation. RESULT: Computed tomography (CT) reported liver metastasis status, carcinoembryonic antigen (CEA) level and differentiation type were identified as risk factors for PCLM in the training set. The final diagnostic model demonstrated good calibration and discrimination with a concordance index of 0.97 and had a robust internal validation. The score ability to diagnose PCLM was further externally validated in SYSMH and GDGH with a concordance index of 0.93. The model showed better calibration and discrimination than CT, CEA and differentiation in each cohort. CONCLUSION: Based on a large multi-institution database and on the routinely observed CT-reported status, CEA level and tumor differentiation in clinical practice, we developed and validated a novel nomogram to predict PLCM.

Expression of the PTEN/FOXO3a/PLZF signalling pathway in pancreatic cancer and its significance in tumourigenesis and progression.

Pancreatic cancer (PC) is one of the most lethal gastrointestinal malignancies. The PTEN/AKT signalling pathway is closely related to the tumourigenesis and progression of PC. The downstream effectors, FOXO3a, PLZF and VEGF, are reported to be involved in angiogenesis, lymph node metastasis and poor survival in PC. By using tissue microarrays and immunohistochemistry, we found, that PTEN, FOXO3a and PLZF expression was significantly decreased in PC specimens compared with that in chronic pancreatitis (CP) specimens, while VEGF expression was significantly increased. Furthermore, the expression of PTEN was positively correlated with that of FOXO3a and PLZF but negatively correlated with that of VEGF. Our results suggest that the PTEN/FOXO3a/PLZF signalling pathway may negatively regulate VEGF expression in PC. Through clinical analysis of 69 PC patients, PTEN, FOXO3a and PLZF expression was found to be significantly decreased in specimens from PC patients with lymph node metastasis and poor prognosis, while VEGF expression was significantly increased. Taken together, these reaults suggest that the PTEN/FOXO3a/PLZF signalling pathway may be capable of inhibiting growth and metastasis in PC by regulating VEGF-mediated angiogenesis, which requires further in vivo and in vitro studies and can potentially be a therapeutic target for PC.

In situ interface engineering for probing the limit of quantum dot photovoltaic devices.

Quantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO2-nanowire/CdSe-QD heterojunction solar cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single nanowire solar cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust 'nanolab' platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale solar cells.

Novel Interface in CuAg Nanostructure Induced by Size Effect.

Bimetallic Janus nanostructures (JNs) have been revealed to be valuable materials because they have unique intermetallic interfaces that enable their potential use in a range of applications. However, with the increasing miniaturization of electronic devices, particle sizes influence the structure and orientation of these heterointerfaces, which plays a significant role in their application. Our in situ annealing experiments with high-resolution transmission electron microscopy have shown that for particle sizes in the sub-10 nm range, CuAg JNs preferentially show a Cu(100)/Ag(100) interface, differing from the larger CuAg JNs, where the Cu(111)/Ag(111) interface is favored. We discuss a feasible atomic motion mechanism to explain the effect of particle size on the formation of different heterointerfaces. Our results reveal the presence of a novel sub-10 nm heterostructure with a unique Cu(100)/Ag(100) interface and also provide crucial insights into understanding the role of particle size in interfacial evolution during thermal annealing of heterostructures.