Metallic Hydrogen in Atomically Precise Gold Nanoclusters

Hu, Guoxiang,Tang, Qing,Lee, Dongil,Wu, Zili,Jiang, De-en American Chemical Society 2017 Chemistry of materials Vol.29 No.11

<P>Hydrogen-metal interaction is the foundation of many technologies and processes, but how hydrogen behaves in atomically precise gold nanoclusters remains unknown even though they have been used in hydrogenation catalysis and water splitting. Herein, we investigate how hydrogen interacts with [Au-25(SR)(18)](q) dusters and mono-atom-doped bimetallic [M1Au24(SR)(18)](q) clusters (M = Pt, Pd, Ag, Cu, Hg, or Cd) from first principles. We find that hydrogen behaves as a metal in these clusters and contributes its is electron to the superatomic free-electron count. This opposite behavior compared to that of the hydride in Cu and Ag dusters allows the small hydrogen to interstitially dope the gold dusters and tune their superatomic electronic structure. The doping energetics shows that when an eight-electron superatom is formed after H doping, the binding energy of H is much stronger, while binding of H with an already eight-electron superatom is much weaker. Indeed, frontier orbitals and the HOMO-LUMO gaps of [Au25H1(SR)(18)](0), [Au25H2(SR)(18)](+) [PtAu24H2(SR)(18)](0), [PdAu24H2(SR)(18)](0), [AgAu24H(SR)(18)](0), and [CuAu24H(SR)(18)](0) all have very similar features, because they are all eight-electron superatoms. By calculating the Gibbs free energies of hydrogen adsorption, we predict that PtAu24(SR)(18), PdAu24(SR)(18), and center-doped CuAu24(SR)(18) can be good electrocatalysts for the hydrogen evolution reaction.</P>

Effects of Metal-Doping on Hydrogen Evolution Reaction Catalyzed by MAu₂₄ and M₂Au₃₆ Nanoclusters (M = Pt, Pd)

Choi, Woojun,Hu, Guoxiang,Kwak, Kyuju,Kim, Minseok,Jiang, De-en,Choi, Jai-Pil,Lee, Dongil American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.51

<P>This paper describes the effects of doped metals on hydrogen evolution reaction (HER) electrocatalyzed by atomically controlled MAu<SUB>24</SUB> and M<SUB>2</SUB>Au<SUB>36</SUB> nanoclusters, where M = Pt and Pd. HER performances, such as onset potential (<I>E</I><SUB>onset</SUB>), catalytic current density, and turnover frequency (TOF), are comparatively examined with respect to the doped metals. Doping Pt or Pd into gold nanoclusters not only changes the electrochemical redox potentials of nanoclusters but also considerably improves the HER activities. <I>E</I><SUB>onset</SUB> is found to be controlled by the nanocluster’s reduction potential matching the reduction potential of H<SUP>+</SUP>. The higher catalytic current and TOF are observed with the doped nanoclusters in the order of PtAu<SUB>24</SUB> > PdAu<SUB>24</SUB> > Au<SUB>25</SUB>. The same trend is observed with the Au<SUB>38</SUB> group (Pt<SUB>2</SUB>Au<SUB>36</SUB> > Pd<SUB>2</SUB>Au<SUB>36</SUB>> Au<SUB>38</SUB>). Density functional theory calculations have revealed that the hydrogen adsorption free energy (Δ<I>G</I><SUB>H</SUB>) is significantly lowered by metal-doping in the order of Au<SUB>25</SUB> > PdAu<SUB>24</SUB> > PtAu<SUB>24</SUB> and Au<SUB>38</SUB> > Pd<SUB>2</SUB>Au<SUB>36</SUB> > Pt<SUB>2</SUB>Au<SUB>36</SUB>, indicating that hydrogen adsorption on the active site of nanocluster is thermodynamically favored by Pd-doping and further by Pt-doping. The doped metals, albeit buried in the core of the nanoclusters, have profound impact on their HER activities by altering their reduction potentials and hydrogen adsorption free energies.</P> [FIG OMISSION]</BR>

The Investigation on Thermal Aging Characteristics of Oil-Paper Insulation in Bushing

Rui-jin Liao,En-de Hu,Li-jun Yang,Zuo-ming Xu 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.3

Bushing is the key link to connect outer and inner insulating systems and also the essential electric accessory in electric power system, especially in the high voltage engineering (AC 1000kV, DC 800kV). This paper presented the experimental research of thermal aging characteristic of oilpaper insulation used in bushing. A thermally accelerated aging experiment at 90℃ was performed. The bushing models containing five layers of paper were sealed into the aging vessels and further aged for 250 days. Then several important parameters associated with the aging were observed and evaluated. The results showed that the degree of polymerization (DP) of papers gradually decreased. The DP values of outermost layer and middle layer fit well into the second-order kinematic model and first-order kinematic model, respectively. Less deterioration speed of the inter-layer paper than outer layer was confirmed by the variation of DP. Hydrolysis was considered as the main cause to this phenomenon. In addition, the logarithm of the furfural concentrations in insulation oil was found to have good linear relationship with DP of papers. Interestingly, when the aging time is about 250 days and DP is 419, the aging process reaches an inflection point at which the DP approaches the leveling off degree of polymerization (LODP) value. Both tanδ and acid number of oils increased, while surface and volume resistivity of papers decreased. The obtained results demonstrated that thermal aging and moisture absorbed in papers brought great influence to the degradation of insulating paper, leading to rapid decrease of DP and increase of the tanδ . Thus, the bushing should be avoided from damp and real-time monitoring to the variation of tanδ and DP values of paper is an effective way to evaluate the insulation status of bushing.

The Investigation on Thermal Aging Characteristics of Oil-Paper Insulation in Bushing

Liao, Rui-jin,Hu, En-de,Yang, Li-jun,Xu, Zuo-ming The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.3

Bushing is the key link to connect outer and inner insulating systems and also the essential electric accessory in electric power system, especially in the high voltage engineering (AC 1000kV, DC 800kV). This paper presented the experimental research of thermal aging characteristic of oil-paper insulation used in bushing. A thermally accelerated aging experiment at 90℃ was performed. The bushing models containing five layers of paper were sealed into the aging vessels and further aged for 250 days. Then several important parameters associated with the aging were observed and evaluated. The results showed that the degree of polymerization (DP) of papers gradually decreased. The DP values of outermost layer and middle layer fit well into the second-order kinematic model and first-order kinematic model, respectively. Less deterioration speed of the inter-layer paper than outer layer was confirmed by the variation of DP. Hydrolysis was considered as the main cause to this phenomenon. In addition, the logarithm of the furfural concentrations in insulation oil was found to have good linear relationship with DP of papers. Interestingly, when the aging time is about 250 days and DP is 419, the aging process reaches an inflection point at which the DP approaches the leveling off degree of polymerization (LODP) value. Both tanδ and acid number of oils increased, while surface and volume resistivity of papers decreased. The obtained results demonstrated that thermal aging and moisture absorbed in papers brought great influence to the degradation of insulating paper, leading to rapid decrease of DP and increase of the tanδ. Thus, the bushing should be avoided from damp and real-time monitoring to the variation of tanδ and DP values of paper is an effective way to evaluate the insulation status of bushing.

Attenuation of Experimental Autoimmune Hepatitis in Mice with Bone Mesenchymal Stem Cell-Derived Exosomes Carrying MicroRNA-223-3p

Lu, Feng-Bin,Chen, Da-Zhi,Chen, Lu,Hu, En-De,Wu, Jin-Lu,Li, Hui,Gong, Yue-Wen,Lin, Zhuo,Wang, Xiao-Dong,Li, Ji,Jin, Xiao-Ya,Xu, Lan-Man,Chen, Yong-Ping Korean Society for Molecular and Cellular Biology 2019 Molecules and cells Vol.42 No.12

MicroRNA-223-3p (miR-223-3p) is one of the potential microRNAs that have been shown to alleviate inflammatory responses in pre-clinical investigations and is highly encased in exosomes derived from bone mesenchymal stem cells (MSC-exosomes). MSC-exosomes are able to function as carriers to deliver microRNAs into cells. Autoimmune hepatitis is one of the challenging liver diseases with no effective treatment other than steroid hormones. Here, we examined whether MSC-exosomes can transfer miR-223-3p to treat autoimmune hepatitis in an experimental model. We found that MSC-exosomes were successfully incorporated with miR-223-3p and delivered miR-223-3p into macrophages. Moreover, there was no toxic effect of exosomes on the macrophages. Furthermore, treatments of either exosomes or exosomes with miR-223-3p successfully attenuated inflammatory responses in the liver of autoimmune hepatitis and inflammatory cytokine release in both the liver and macrophages. The mechanism may be related to the regulation of miR-223-3p level and STAT3 expression in the liver and macrophages. These results suggest that MSC-exosomes can be used to deliver miR-223-3p for the treatment of autoimmune hepatitis.

Attenuation of Experimental Autoimmune Hepatitis in Mice with Bone Mesenchymal Stem Cell-Derived Exosomes Carrying MicroRNA-223-3p

Yong-Ping Chen,Feng-Bin Lu,Da-Zhi Chen,Lu Chen,En-De Hu,Jin-Lu Wu,Hui Li,Yue-Wen Gong,Zhuo Lin,Xiao-Dong Wang,Ji Li,Xiao-Ya Jin,Lan-Man Xu 한국분자세포생물학회 2019 Molecules and cells Vol.42 No.12

MicroRNA-223-3p (miR-223-3p) is one of the potential microRNAs that have been shown to alleviate inflammatory responses in pre-clinical investigations and is highly encased in exosomes derived from bone mesenchymal stem cells (MSC-exosomes). MSC-exosomes are able to function as carriers to deliver microRNAs into cells. Autoimmune hepatitis is one of the challenging liver diseases with no effective treatment other than steroid hormones. Here, we examined whether MSC-exosomes can transfer miR-223-3p to treat autoimmune hepatitis in an experimental model. We found that MSC-exosomes were successfully incorporated with miR-223-3p and delivered miR-223-3p into macrophages. Moreover, there was no toxic effect of exosomes on the macrophages. Furthermore, treatments of either exosomes or exosomes with miR-223-3p successfully attenuated inflammatory responses in the liver of autoimmune hepatitis and inflammatory cytokine release in both the liver and macrophages. The mechanism may be related to the regulation of miR-223-3p level and STAT3 expression in the liver and macrophages. These results suggest that MSC-exosomes can be used to deliver miR-223-3p for the treatment of autoimmune hepatitis.