Controllable Coordination of Phosphotungstic Acid-Modified Carbon Matrix for Anchoring Different Sizes of Pt Species: From Single Atoms, Subnanoclusters to Nanoparticles

2021 ◽  
Author(s):  
Jiazhe Li ◽  
Zhiyuan Yan ◽  
Lingxiang Bao ◽  
Cheng-Hui Sun ◽  
Si-Ping Pang
Keyword(s):  
Phosphotungstic Acid ◽  
Carbon Matrix ◽  
High Density ◽  
Coordination Environment ◽  
Single Atoms

Pt species with different sizes uniformly dispersed on phosphotungstic (PTA) acid modified carbon matrix (PTA-C) were controllably synthesized by manipulating the coordination environment. The results indicate that high-density and well-defined...

‘Proton Escalator’ PEI and Phosphotungstic Acid Constructing a Nanofiber Membrane with Remarkable Proton Conductivity

2021 ◽  
Author(s):  
Xiuwei Sun ◽  
Shumei Liu ◽  
Qingyin Wu ◽  
Shan Zhang ◽  
Hong-Rui Tian ◽  
...  
Keyword(s):  
Proton Conductivity ◽  
Phosphotungstic Acid ◽  
Proton Conduction ◽  
High Density ◽  
Nanofiber Membrane ◽  
New Type ◽  
High Flexibility

Polyethyleneimine (PEI) is expected to become a new type of proton conduction booster due to its high density amine and extremely high flexibility. Herein, a nanofiber membrane (eHPW-PEI) composed of...

scholarly journals A pyrolysis-free path toward superiorly catalytic nitrogen-coordinated single atom

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw2322 ◽  
Author(s):  
Peng Peng ◽  
Lei Shi ◽  
Feng Huo ◽  
Chunxia Mi ◽  
Xiaohong Wu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Oxygen Reduction ◽  
Structural Changes ◽  
Carbon Matrix ◽  
Single Atom ◽  
Synthetic Approach ◽  
Iron Phthalocyanine ◽  
Practical Applications ◽  
Single Atoms

Nitrogen-coordinated single-atom catalysts (SACs) have emerged as a frontier for electrocatalysis (such as oxygen reduction) with maximized atom utilization and highly catalytic activity. The precise design and operable synthesis of SACs are vital for practical applications but remain challenging because the commonly used high-temperature treatments always result in unpredictable structural changes and randomly created single atoms. Here, we develop a pyrolysis-free synthetic approach to prepare SACs with a high electrocatalytic activity using a fully π-conjugated iron phthalocyanine (FePc)–rich covalent organic framework (COF). Instead of randomly creating Fe-nitrogen moieties on a carbon matrix (Fe-N-C) through pyrolysis, we rivet the atomically well-designed Fe-N-C centers via intermolecular interactions between the COF network and the graphene matrix. The as-synthesized catalysts demonstrate exceptional kinetic current density in oxygen reduction catalysis (four times higher than the benchmark Pt/C) and superior power density and cycling stability in Zn-air batteries compared with Pt/C as air electrodes.

scholarly journals Evaluation of two homogeneous methods for measuring high-density lipoprotein cholesterol

1997 ◽  
Vol 43 (6) ◽  
pp. 1048-1055 ◽  
Author(s):  
Yi-Chang Huang ◽  
Jau-Tsuen Kao ◽  
Keh-Sung Tsai
Keyword(s):  
Polyethylene Glycol ◽  
High Density Lipoprotein ◽  
High Density Lipoprotein Cholesterol ◽  
Phosphotungstic Acid ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
High Density ◽  
Lipoprotein Cholesterol ◽  
Homogeneous Assays ◽  
Better Than

Abstract We evaluated the performance of two homogeneous assays for quantifying HDL cholesterol (HDL-C) and compared them with the phosphotungstic acid (PTA)/MgCl2 assay. Both homogeneous HDL-C assays were precise, having a within-run CV of <1.20% and a between-run CV of <4.07%. The HDL-C values (y) measured by the two homogeneous methods correlated well with those by the PTA/MgCl2 method (x): y = 1.00x + 64.98 mg/L, r = 0.987, Sy|x = 27.99 mg/L (n = 152) for the polyethylene glycol-modified enzymes/α-cyclodextrin sulfate (PEGME) assay (Kyowa), and y = 0.84x + 106.51 mg/L, r = 0.984, Sy|x = 26.10 mg/L (n = 152) for the polyanion–polymer/detergent (PPD) assay (Daiichi). The specificity of the PEGME method seemed better than that of the PPD method, as the PPD method was markedly interfered with by supplemental LDL-C. Addition of 20 g/L triglycerides produced a negative error of ∼18% in both homogeneous assays. Bilirubin and hemoglobin had little influence on the PEGME method; hemoglobin had little effect on the PPD method. Bilirubin, however, markedly decreased the readings by the PPD method. We found the PEGME assay superior to the PPD assay for routine HDL-C testing, because the PPD assay is relatively inaccurate and not specific.

Densitometry of phosphatidylcholine and sphingomyelin in high-density lipoproteins.

1983 ◽  
Vol 29 (7) ◽  
pp. 1435-1437 ◽  
Author(s):  
G Schmitz ◽  
H U Jabs ◽  
G Assmann
Keyword(s):  
Sulfuric Acid ◽  
Phosphotungstic Acid ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Concentrations ◽  
Layer Chromatography ◽  
Inexpensive Technique ◽  
Native Plasma ◽  
Enzymatic Methods

Abstract We describe the quantitative densitometric determination of phosphatidylcholine (PC) and sphingomyelin (SP) in human serum after precipitation with phosphotungstic acid/MgCl2 and use of thin-layer chromatography. After development, chromatographic plates were charred with methanolic sulfuric acid and MnCl2 and scanned by direct reflectance densitometry in an automated densitometric system interfaced to a basic programmable computing integrator. The method is sensitive enough to detect abnormally low concentrations of PC and SP in high-density lipoproteins. The accuracy of the method was tested either with the Bartlett phosphorus assay or with enzymatic methods for PC and SP; correlations of the described method with the enzymatic determinations were r = 0.93 and 0.88, respectively. Day-to-day precision (CV) for the phospholipid determination was 8.6% for PC and 12.2% for SP. The major advantage of this inexpensive technique is that native plasma or serum or the serum supernate after precipitation can be used without prior delipidation. With this technique serum high-density lipoproteins had PC values of 1.08 (SD 0.32) mmol/L in men (n = 158) and 1.12 (SD 0.37) mmol/L in women (n = 192); similarly, SP values were 0.23 (SD 0.07) mmol/L in the men and 0.23 (SD 0.08) mmol/L in the women. The differences by sex are not significant.

scholarly journals The Challenge of Achieving a High Density of Fe-Based Active Sites in a Highly Graphitic Carbon Matrix

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 144 ◽  
Author(s):  
Jingkun Li ◽  
Qingying Jia ◽  
Sanjeev Mukerjee ◽  
Moulay-Tahar Sougrati ◽  
Goran Drazic ◽  
...  
Keyword(s):  
Porous Structure ◽  
Active Sites ◽  
Carbon Matrix ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
High Specific Surface Area ◽  
High Density ◽  
Graphitic Carbon ◽  
High Degree ◽  
Degree Of Graphitization

As one of the most promising platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR), Fe–N–C catalysts with a high density of FeNx moieties integrated in a highly graphitic carbon matrix with a proper porous structure have attracted extensive attention to combine the high activity, high stability and high accessibility of active sites. Herein, we investigated a ZnCl2/NaCl eutectic salts-assisted ionothermal carbonization method (ICM) to synthesize Fe–N–C catalysts with tailored porous structure, high specific surface area and a high degree of graphitization. However, it was found to be challenging to anchor a high density of FeNx sites onto highly graphitized carbon. Iron precursors with preexisting Fe–N coordination were required to form FeNx sites in the nitrogen-doped carbon with a high degree of graphitization, while individual Fe and N precursors led to a Fe–N–C catalyst with poor-ORR activity. This provides valuable insights into the synthesis-structure relationship. Moreover, the FeNx moieties were identified as the major active sites in acidic conditions, while both FeNx sites and Fe2O3 were found to be active in alkaline medium.

Quantification of high-density-lipoprotein cholesterol by precipitation with phosphotungstic acid/MgCl2.

1983 ◽  
Vol 29 (12) ◽  
pp. 2026-2030 ◽  
Author(s):  
G Assmann ◽  
H Schriewer ◽  
G Schmitz ◽  
E O Hägele
Keyword(s):  
High Density Lipoprotein ◽  
High Performance ◽  
Phosphotungstic Acid ◽  
Density Lipoprotein ◽  
High Density ◽  
Precipitation Method ◽  
Lipoprotein Subfractions ◽  
Precipitation Procedure ◽  
High Density Lipoprotein Subfractions ◽  
Layer Chromatography

Abstract We evaluated the use of a modified phosphotungstic acid/MgCl2 precipitation procedure for the precipitation of apolipoprotein B-containing lipoproteins. Precipitation of these lipoproteins [very-low- and low-density lipoproteins, and lipoprotein (a)] is complete, with negligible coprecipitation of high-density lipoprotein subfractions (HDL1, HDL2, HDL3), even in hypertriglyceridemic sera. In comparison with ultracentrifugation, the precipitation method yields, on the average, values that are 0.17 mmol/L lower for cholesterol values but almost identical for apolipoprotein A-I and phosphatidylcholine. Looking for delta 3,5-cholestadiene formed from cholesterol in the precipitation residue, we used "high-performance" liquid chromatography and "high-performance" thin-layer chromatography and found none.

scholarly journals Achieving an exceptionally high loading of isolated cobalt single atoms on a porous carbon matrix for efficient visible-light-driven photocatalytic hydrogen production

2019 ◽  
Vol 10 (9) ◽  
pp. 2585-2591 ◽  
Author(s):  
Rui Shi ◽  
Chengcheng Tian ◽  
Xiang Zhu ◽  
Cheng-Yun Peng ◽  
Bingbao Mei ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Visible Light ◽  
Porous Carbon ◽  
Carbon Matrix ◽  
High Loading ◽  
Photocatalytic Hydrogen Production ◽  
Single Atoms ◽  
Visible Light Driven ◽  
Preparation Strategy

Isolated cobalt single atoms with a high loading of 5.9 wt% are generated through an in situ preparation strategy.

Platinum nanoclusters in doped glassy carbon: An EM investigation

1992 ◽  
Vol 50 (1) ◽  
pp. 300-301
Author(s):  
Richard J. Spontak ◽  
Michael E. Huston ◽  
Nicolas L. Pocard ◽  
Matthew R. Callstrom
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sol Gel ◽  
Carbon Matrix ◽  
Single Atoms ◽  
Transmission Electron ◽  
Metal Evaporation ◽  
Molecular Catalysis ◽  
Rigid Matrix ◽  
Platinum Nanoclusters

Fabrication of materials which possess a fine dispersion of nanoscale metallic clusters (referred to here as nanoclusters) is of both commercial and fundamental importance. The relatively large surface area of these particulates makes them particularly attractive for applications in molecular catalysis and microelectronics. From a more fundamental viewpoint, they collectively represent structural intermediates between single atoms and crystalline solids. Efforts designed to produce metallic nanoclusters systematically on specific surfaces or in bulk media have relied on a variety of techniques, such as metal evaporation and sol-gel processes, just to name two. Recent efforts have shown that thermolysis of platinum-containing carbon precursors results in Pt(0) nanoclusters dispersed within a stable conductive carbon matrix. These doped materials, at only 1 atom% Pt, exhibit voltammetric responses for H+ and O2 similar to those of pure platinum while remaining significantly more stable (presumably due to the rigid matrix). The focus of the present work is to employ transmission electron microscopy (TEM) to correlate the characteristics of these nanoclusters with conditions of preparation.

2D-organic framework confined metal single atoms with the loading reaching the theoretical limit

2020 ◽  
Vol 7 (10) ◽  
pp. 2726-2733
Author(s):  
Chao Lin ◽  
Hao Zhang ◽  
Xiaokai Song ◽  
Dong-Hyung Kim ◽  
Xiaopeng Li ◽  
...  
Keyword(s):  
Air Flow ◽  
High Density ◽  
Single Atom ◽  
Theoretical Limit ◽  
Single Atoms ◽  
Synthetic Strategy ◽  
Flow Batteries ◽  
Organic Framework

A synthetic strategy utilizing a predesigned organic framework is demonstrated to construct high-density single-atom catalysts for long-lasting zinc–air flow batteries.

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