Atomic Resolution Scanning Transmission Electron Microscopy of Two-Dimensional Layered Transition Metal Dichalcogenides

Lu, Ning,Wang, Jinguo,Oviedo, uan Pablo,Lian, Guoda,Kim, Moon Jea Korean Society of Microscopy 2015 Applied microscopy Vol.45 No.4

Transition metal dichalcogenides (TMDs) are a class of two-dimensional (2D) materials that have attracted growing interest because of their promising applications. The properties of TMDs strongly depend on the crystalline structure and the number and stacking sequence of layers in their crystals and thin films. Though electrical, mechanical, and magnetic studies of 2D materials are being conducted, there is an evident lack of direct atom-by-atom visualization, limiting insight on these highly exciting material systems. Herein, we present our recent studies on the characterization of 2D layered materials by means of aberration corrected scanning transmission electron microscopy (STEM), in particular via high angle annular dark field (HAADF) imaging. We have identified the atomic arrangements and defects in 2H stacked TMDs, 1T stacked TMDs, distorted 1T stacked TMDs, and vertically integrated heterojunctions of 2D TMDs crystals.

Control Over the Branched Structures of Platinum Nanocrystals for Electrocatalytic Applications

Ma, Liang,Wang, Chengming,Gong, Ming,Liao, Lingwen,Long, Ran,Wang, Jinguo,Wu, Di,Zhong, Wei,Kim, Moon J.,Chen, Yanxia,Xie, Yi,Xiong, Yujie American Chemical Society 2012 ACS NANO Vol.6 No.11

<P>Structural control of branched nanocrystals allows tuning two parameters that are critical to their catalytic activitythe surface-to-volume ratio, and the number of atomic steps, ledges, and kinks on surface. In this work, we have developed a simple synthetic system that allows tailoring the numbers of branches in Pt nanocrystals by tuning the concentration of additional HCl. In the synthesis, HCl plays triple functions in tuning branched structures <I>via</I> oxidative etching: (i) the crystallinity of seeds and nanocrystals; (ii) the number of {111} or {100} faces provided for growth sites; (iii) the supply kinetics of freshly formed Pt atoms in solution. As a result, tunable Pt branched structurestripods, tetrapods, hexapods, and octopods with identical chemical environmentcan be rationally synthesized in a single system by simply altering the etching strength. The controllability in branched structures enables to reveal that their electrocatalytic performance can be optimized by constructing complex structures. Among various branched structures, Pt octopods exhibit particularly high activity in formic acid oxidation as compared with their counterparts and commercial Pt/C catalysts. It is anticipated that this work will open a door to design more complex nanostructures and to achieve specific functions for various applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-11/nn304237u/production/images/medium/nn-2012-04237u_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn304237u'>ACS Electronic Supporting Info</A></P>

Copper Can Still Be Epitaxially Deposited on Palladium Nanocrystals To Generate Core–Shell Nanocubes Despite Their Large Lattice Mismatch

Jin, Mingshang,Zhang, Hui,Wang, Jinguo,Zhong, Xiaolan,Lu, Ning,Li, Zhiyuan,Xie, Zhaoxiong,Kim, Moon J.,Xia, Younan American Chemical Society 2012 ACS NANO Vol.6 No.3

<P>Here we report the synthesis of Pd@Cu core–shell nanocubes <I>via</I> epitaxial growth, where the lattice mismatch is 7.1%. The synthesis involved the use of Pd seeds with different shapes (including cubes, cuboctahedra, and octahedra) for the epitaxial growth of Cu shells. Different from the conventional growth mode, Cu atoms initially nucleated only on a few of the many faces of a Pd seed, onto which more Cu atoms were continuously added to generate Cu blocks. Later, the Cu atoms also started to nucleate and grow on other faces of the Pd seed until the entire surface of the seed was covered by a Cu shell. As a result, the Pd seed was rarely located in the center of each core–shell structure. The final product took a cubic shape enclosed by {100} facets regardless of the type of Pd seeds used because of the selective capping of Cu(100) surface by hexadecylamine. The edge lengths of the Pd@Cu nanocubes could be tuned from 50 to 100 nm by varying the amount of Pd seeds while keeping the amount of CuCl<SUB>2</SUB> precursor.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-3/nn2050278/production/images/medium/nn-2011-050278_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn2050278'>ACS Electronic Supporting Info</A></P>

Therapeutic effects of traditional Chinese medicine (Maxingshigan-Weijing Decoction) on COVID-19: An open-label randomized controlled trial

Congcong Zeng,Zhengzhong Yuan,Jiahui Zhu,Yintong Wang,Yongyong Xie,Ren Ye,Jinguo Cheng 한국한의학연구원 2021 Integrative Medicine Research Vol.10 No.-

Background Wenzhou has achieved great progress in the prevention and control of the growing coronavirus disease 2019 (COVID-19) pandemic, and traditional Chinese medicine (TCM) has played an indispensable role in this fight. This study aimed to investigate the efficacy of Maxingshigan-Weijing decoction (MWD) in treating infected patients. Methods This study was an open-label randomized controlled trial. Inpatients with mild or moderate symptoms caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were randomly treated with routine supportive care alone or a combination of routine supportive care and MWD. The primary outcome was the rate of symptom (fever, fatigue, cough and difficulty breathing) recovery. Results Fifty-nine inpatients were enrolled, of whom 29 received routine supportive care alone (control group) and 30 received combination therapy (treatment group). The rate of symptom recovery was significantly higher in the treatment group than in the control group. The time to recovery of fever (3 vs. 7 days), fatigue (9 vs. 12 days), coughing (9 vs. 14 days) and difficulty breathing (4.5 vs. 9.5 days) was also significantly shorter in the treatment group (all p < 0.001). The syndrome score was lower after MWD treatment. However, neither group differed in the viral assay findings, hospitalization days, medication time or the rate of conversion to severe cases. Conclusions MWD increased the rate of symptom recovery and shortened the time to recovery of clinical symptoms without deterioration to death or critical care. These findings may provide opportunities for the use of complementary medicine in treating this infection. Clinical trial registration Chinese Clinical Trial Registry, ChiCTR2000030759. Background Wenzhou has achieved great progress in the prevention and control of the growing coronavirus disease 2019 (COVID-19) pandemic, and traditional Chinese medicine (TCM) has played an indispensable role in this fight. This study aimed to investigate the efficacy of Maxingshigan-Weijing decoction (MWD) in treating infected patients. Methods This study was an open-label randomized controlled trial. Inpatients with mild or moderate symptoms caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were randomly treated with routine supportive care alone or a combination of routine supportive care and MWD. The primary outcome was the rate of symptom (fever, fatigue, cough and difficulty breathing) recovery. Results Fifty-nine inpatients were enrolled, of whom 29 received routine supportive care alone (control group) and 30 received combination therapy (treatment group). The rate of symptom recovery was significantly higher in the treatment group than in the control group. The time to recovery of fever (3 vs. 7 days), fatigue (9 vs. 12 days), coughing (9 vs. 14 days) and difficulty breathing (4.5 vs. 9.5 days) was also significantly shorter in the treatment group (all p < 0.001). The syndrome score was lower after MWD treatment. However, neither group differed in the viral assay findings, hospitalization days, medication time or the rate of conversion to severe cases. Conclusions MWD increased the rate of symptom recovery and shortened the time to recovery of clinical symptoms without deterioration to death or critical care. These findings may provide opportunities for the use of complementary medicine in treating this infection. Clinical trial registration Chinese Clinical Trial Registry, ChiCTR2000030759.

Vertebral Artery Variations at the Craniovertebral Junction in “Sandwich” Atlantoaxial Dislocation Patients

Yinglun Tian,Nanfang Xu,Ming Yan,Jinguo Chen,Kan-Lin Hung,Xiangyu Hou,Shenglin Wang,Weishi Li 대한척추신경외과학회 2021 Neurospine Vol.18 No.4

Objective: To summarize the vertebral artery (VA) pattern of 96 “sandwich” atlantoaxial dislocation (AAD) patients and to describe the strategies of reducing the injury of VA during surgery. Methods: From 2009 to 2020, we retrospectively reviewed the 3-dimensional computed tomography angiography data of 96 AAD patients combined with atlas occipitalization and C2–3 fusion, which were diagnosed as “sandwich” AAD and 96 patients as control group patients who were without atlas occipitalization, C2–3 fusion and any other cervical bone deformity at our institution. The variations of each side of VA were described in 3 different parts (C0–1, C1–2, and C2–3) according to the characteristics of the 3-part pathological structures in “sandwich” subgroup. Results: One hundred ninety-two sides of VAs in every group of patients were analyzed and every VA was described separately at 3 different level regions. There were different variations in these 3 different regions: 4 variations in the upper fusion region, 5 variations in the sandwiched region, and 6 variations in the lower fusion region in sandwich AAD patients. And the rate of VA deformity in sandwich AAD patients was much higher and more types of VA variations existed. Conclusion: In “sandwich” AAD patients, deformities of vertebral arteries in craniovertebral junction are more common, and the same VA may have deformities at different levels that severely affect surgical procedures. Therefore, preoperative imaging examination of VA for “sandwich” AAD patients is vital of guiding surgeons to avoid injury of VA during surgery.

On Synergistic Effects of Hierarchical γ′ Precipitates and Discontinuous Plastic Flow in a Ni-based Single Crystal Superalloy with an [001] Orientation

Yunling Du,Yanhong Yang,Shuai Guan,Xinguang Wang,Chuanyong Cui,Jinguo Li,Yizhou Zhou,Xiaofeng Sun 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1

A discontinuous plastic flow is detected in a single-crystal superalloy with an [001] orientation during tensile tests over a wide temperature range. Results reveals that the synergistic impact of normal γ′ precipitates and nanoscale γ′ precipitates in γ matrix on the dislocations motion is the root of the serrated flow.

Experimental study and numerical simulation on springback of Ti-6Al-4V alloy under hot U-bending

Fen-Qiang Li,Jishuai Jiang,Juemei Wang,Jinguo Wang,Xinyu Chen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.7

In this study, springback of Ti-6Al-4V sheet subjected to hot bending was investigated experimentally and by numerical simulation. The experiment determined the relative effects of forming temperature, forming speed and holding time on springback during hot bending of the alloy sheet. Distribution of temperature and equivalent stress fields experienced during hot bending were predicted by thermal-mechanical coupling numerical simulation. Analysis of the mutual influence of deformation and temperature was conducted using finite element modeling in DYNAFORM software. The results indicated that increased forming temperature, forming speed and holding time each reduced springback to a degree. Forming temperature had the greatest influence in limiting springback, followed by forming speed and holding time, the latter of which was of minor significance. The thermomechanical coupling numerical model is reliable and the predicted temperature field distribution was confirmed.

On the role of surface diffusion in determining the shape or morphology of noble-metal nanocrystals

Xia, Xiaohu,Xie, Shuifen,Liu, Maochang,Peng, Hsin-Chieh,Lu, Ning,Wang, Jinguo,Kim, Moon J.,Xia, Younan National Academy of Sciences 2013 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.110 No.17

<P>Controlling the shape or morphology of metal nanocrystals is central to the realization of their many applications in catalysis, plasmonics, and electronics. In one of the approaches, the metal nanocrystals are grown from seeds of certain crystallinity through the addition of atomic species. In this case, manipulating the rates at which the atomic species are added onto different crystallographic planes of a seed has been actively explored to control the growth pattern of a seed and thereby the shape or morphology taken by the final product. Upon deposition, however, the adsorbed atoms (adatoms) may not stay at the same sites where the depositions occur. Instead, they can migrate to other sites on the seed owing to the involvement of surface diffusion, and this could lead to unexpected deviations from a desired growth pathway. Herein, we demonstrated that the growth pathway of a seed is indeed determined by the ratio between the rates for atom deposition and surface diffusion. Our result suggests that surface diffusion needs to be taken into account when controlling the shape or morphology of metal nanocrystals.</P>

Atomic Layer-by-Layer Deposition of Platinum on Palladium Octahedra for Enhanced Catalysts toward the Oxygen Reduction Reaction

Park, Jinho,Zhang, Lei,Choi, Sang-Il,Roling, Luke T.,Lu, Ning,Herron, Jeffrey A.,Xie, Shuifen,Wang, Jinguo,Kim, Moon J.,Mavrikakis, Manos,Xia, Younan American Chemical Society 2015 ACS NANO Vol.9 No.3

<P>We systematically evaluated two different approaches to the syntheses of Pd@Pt<SUB><I>n</I>L</SUB> (<I>n</I> = 2–5) core–shell octahedra. We initially prepared the core–shell octahedra using a polyol-based route by titrating a Pt(IV) precursor into the growth solution containing Pd octahedral seeds at 200 °C through the use of a syringe pump. The number of Pt atomic layers could be precisely controlled from two to five by increasing the volume of the precursor solution while fixing the amount of seeds. We then demonstrated the synthesis of Pd@Pt<SUB><I>n</I>L</SUB> octahedra using a water-based route at 95 °C through the one-shot injection of a Pt(II) precursor. Due to the large difference in reaction temperature, the Pd@Pt<SUB><I>n</I>L</SUB> octahedra obtained <I>via</I> the water-based route showed sharper corners than their counterparts obtained through the polyol-based route. When compared to a commercial Pt/C catalyst based upon 3.2 nm Pt particles, the Pd@Pt<SUB><I>n</I>L</SUB> octahedra prepared using both methods showed similar remarkable enhancement in terms of activity (both specific and mass) and durability toward the oxygen reduction reaction. Calculations based upon periodic, self-consistent density functional theory suggested that the enhancement in specific activity for the Pd@Pt<SUB><I>n</I>L</SUB> octahedra could be attributed to the destabilization of OH on their Pt<SUB><I>n</I>L</SUB>*/Pd(111) surface relative to the {111} and {100} facets exposed on the surface of Pt/C. The destabilization of OH facilitates its hydrogenation, which was found to be the rate-limiting step of the oxygen reduction reaction on all these surfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-3/nn506387w/production/images/medium/nn-2014-06387w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn506387w'>ACS Electronic Supporting Info</A></P>

Synthesis and Characterization of 9 nm Pt–Ni Octahedra with a Record High Activity of 3.3 A/mg_Pt for the Oxygen Reduction Reaction

Choi, Sang-Il,Xie, Shuifen,Shao, Minhua,Odell, Jonathan H.,Lu, Ning,Peng, Hsin-Chieh,Protsailo, Lesia,Guerrero, Sandra,Park, Jinho,Xia, Xiaohu,Wang, Jinguo,Kim, Moon J.,Xia, Younan American Chemical Society 2013 Nano letters Vol.13 No.7

<P>Nanoscale Pt–Ni bimetallic octahedra with controlled sizes have been actively explored in recent years owning to their outstanding activity for the oxygen reduction reaction (ORR). Here we report the synthesis of uniform 9 nm Pt–Ni octahedra with the use of oleylamine and oleic acid as surfactants and W(CO)<SUB>6</SUB> as a source of CO that can promote the formation of {111} facets in the presence of Ni. Through the introduction of benzyl ether as a solvent, the coverage of both surfactants on the surface of resultant Pt–Ni octahedra was significantly reduced while the octahedral shape was still attained. By further removing the surfactants through acetic acid treatment, we observed a specific activity 51-fold higher than that of the state-of-the-art Pt/C catalyst for the ORR at 0.93 V, together with a record high mass activity of 3.3 A mg<SUB>Pt</SUB><SUP>–1</SUP> at 0.9 V (the highest mass activity reported in the literature was 1.45 A mg<SUB>Pt</SUB><SUP>–1</SUP>). Our analysis suggests that this great enhancement of ORR activity could be attributed to the presence of a clean, well-preserved (111) surface for the Pt–Ni octahedra.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-7/nl401881z/production/images/medium/nl-2013-01881z_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl401881z'>ACS Electronic Supporting Info</A></P>