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1.
Cell Death Dis ; 11(1): 35, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31959742

RESUMO

Vascular smooth muscle cell (SMC) from arterial stenotic-occlusive diseases is featured with deficiency in mitochondrial respiration and loss of cell contractility. However, the regulatory mechanism of mitochondrial genes and mitochondrial energy metabolism in SMC remains elusive. Here, we described that DNA methyltransferase 1 (DNMT1) translocated to the mitochondria and catalyzed D-loop methylation of mitochondrial DNA in vascular SMCs in response to platelet-derived growth factor-BB (PDGF-BB). Mitochondrial-specific expression of DNMT1 repressed mitochondrial gene expression, caused functional damage, and reduced SMC contractility. Hypermethylation of mitochondrial D-loop regions were detected in the intima-media layer of mouse carotid arteries subjected to either cessation of blood flow or mechanical endothelial injury, and also in vessel specimens from patients with carotid occlusive diseases. Likewise, the ligated mouse arteries exhibited an enhanced mitochondrial binding of DNMT1, repressed mitochondrial gene expression, defects in mitochondrial respiration, and impaired contractility. The impaired contractility of a ligated vessel could be restored by ex vivo transplantation of DNMT1-deleted mitochondria. In summary, we discovered the function of DNMT1-mediated mitochondrial D-loop methylation in the regulation of mitochondrial gene transcription. Methylation of mitochondrial D-loop in vascular SMCs contributes to impaired mitochondrial function and loss of contractile phenotype in vascular occlusive disease.

2.
Nanoscale ; 12(3): 1673-1679, 2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31894217

RESUMO

Ribonuclease H (RNase H), an intracellular ribonuclease, plays a crucial role in cellular processes and especially relates to many disease processes. Here, we report a novel signal amplification strategy based on an RNase H-powered DNA walking machine for specific and sensitive RNase H activity detection. The DNA walking machine is composed of a small quantity of DNA walker strands and abundant FAM-labeled DNA-RNA chimeric strands on a single gold nanoparticle (AuNP). RNase H can specifically degrade the RNA fragment in a DNA-RNA hybrid duplex and trigger the autonomous movement of a DNA walker strand on the AuNP surface. During this process, each step of the walking can release the FAM-labeled RNA from the surface of the AuNP, realizing the signal amplification for RNase H sensing. This method has been successfully utilized for RNase H activity detection in a complex system and applied for screening of related inhibitors. Therefore, our RNase H-powered DNA walking machine gives a novel platform for RNase H activity detection and RNase H-associated drug discovery.

3.
Acta Pharmacol Sin ; 41(1): 101-109, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31534200

RESUMO

Monoclonal antibodies are believed to be magic bullets and hold great potential for lots of biological process. About 100 µg of mAb109 was expressed in 5 × 106 cells after 10 days' immunization. 64Cu-NOTA-mAb109 was synthesized with the specific activity of 0.74 MBq/µg and high in vitro stability. The binding affinity of 64Cu-NOTA-mAb109 in A549 cells was determined to be 29.64 nM. 64Cu-NOTA-mAb109 displayed prominent tumor accumulation from 2 h to 60 h p.i. (9.34 ± 0.67 %ID/g). NIRF imaging of Cy5.5-mAb109 showed high accumulation till 9 days p.i., while tumors nearly can not be observed in negative groups, which was confirmed by autoradiography. Immunohistological study confirmed that mAb109 had strong and specific capacity to bind lung adenocarcinoma (concentration to 58 nM). Our study demonstrated mAb109 was a new platform for the development of novel agent for lung adenocarcinoma noninvasive imaging. The resulted 64Cu-NOTA-mAb109/Cy5.5-mAb109 show favorable imaging properties/specificity for A549 tumor and high sensitivity to human lung adenocarcinoma tissues.

4.
Oncol Rep ; 43(1): 260-269, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31746437

RESUMO

The aim of the present study was to investigate the synergistic antitumor effects of emodin and 3'­azido­3'­deoxythymidine (AZT) on human chronic myeloid leukemia cells and to explore the possible underlying mechanisms. The K562 cells were treated with emodin and AZT, and the rates of cell inhibition and apoptosis were determined by MTT assay and flow cytometry, respectively. The mRNA expression of EGR1 was detected by reverse transcription­polymerase chain reaction (RT­PCR) analysis. The expression of EGR1 was silenced using siRNA, and then protein expression of ß­catenin was detected by western blotting. The results demonstrated that AZT enhanced the inhibitory effect of emodin in K562 cells. The IC50 of the emodin/AZT combination at 24, 48 or 72 h was 23.6/235.6, 10.2/101.6 or 5.9/58.5 µmol/l, respectively, which was significantly lower compared with the IC50 of emodin (all >32 µmol/l) or AZT (all >320 µmol/l) alone. There was a dose­dependent response to the combined emodin and AZT treatment, and the calculation of the combination index yielded values <1, demonstrating the synergistic effect of the combined treatment compared with the control (P<0.05). Furthermore, the combination of emodin and AZT increased apoptosis in K562 cells (P<0.05). Apoptosis was higher in the combination group compared with that of either treatment alone or control groups. The expression of early growth response­1 (EGR1) in K562 cells was upregulated in a time­dependent manner. The expression of EGR1 was higher in the combination group compared with that in the emodin or AZT alone groups. The expression of the Wnt/ß­catenin signaling pathway in the combination group was lower compared with that in the emodin or AZT alone groups. The expression of the Wnt/ß­catenin signaling pathway was significantly increased following EGR1 siRNA transfection. These data suggest that treating K562 cells with a combination of emodin and AZT exhibits reduced toxicity and improves therapeutic efficacy, and that the growth, inhibition, apoptosis and regulation of the Wnt/ß­catenin signaling pathway in human chronic myeloid leukemia cells by emodin and AZT may be associated with the expression of EGR1.

5.
Angew Chem Int Ed Engl ; 59(8): 3058-3062, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31821697

RESUMO

We herein report a general organocatalytic enantioselective strategy for the construction of highly strained spiro[2,3]hexane skeletons from methylenecyclopropanes and a broad selection of α,ß-unsaturated aldehydes. The reaction proceeds through a Michael addition followed by ring expansion of methylenecyclopropanes and nucleophilic attack of an enamine to realize the construction of spiro[2,3]hexanes. Key to the success of this approach are the utilization of an electron-deficient difluoro-substituted secondary amine catalyst and the intrinsic reactivity of methylenecyclopropanes.

6.
Chem Commun (Camb) ; 56(4): 639-642, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31833487

RESUMO

In this work, we have developed a novel DNAzyme motor initiated by endogenous enzyme for sensitive imaging of intracellular RNase H activity.


Assuntos
DNA Catalítico/metabolismo , Imagem Óptica , Ribonuclease H/metabolismo , Sobrevivência Celular , Células HeLa , Células Hep G2 , Humanos , Células MCF-7 , Microscopia Confocal , Microscopia de Fluorescência
7.
Nat Commun ; 10(1): 5599, 2019 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-31811129

RESUMO

Efficient generation of hydrogen from water-splitting is an underpinning chemistry to realize the hydrogen economy. Low cost, transition metals such as nickel and iron-based oxides/hydroxides have been regarded as promising catalysts for the oxygen evolution reaction in alkaline media with overpotentials as low as ~200 mV to achieve 10 mA cm-2, however, they are generally unsuitable for the hydrogen evolution reaction. Herein, we show a Janus nanoparticle catalyst with a nickel-iron oxide interface and multi-site functionality for a highly efficient hydrogen evolution reaction with a comparable performance to the benchmark platinum on carbon catalyst. Density functional theory calculations reveal that the hydrogen evolution reaction catalytic activity of the nanoparticle is induced by the strong electronic coupling effect between the iron oxide and the nickel at the interface. Remarkably, the catalyst also exhibits extraordinary oxygen evolution reaction activity, enabling an active and stable bi-functional catalyst for whole cell water-splitting with, to the best of our knowledge, the highest energy efficiency (83.7%) reported to date.

8.
Chem Commun (Camb) ; 55(92): 13832-13835, 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31681921

RESUMO

The first example of the preparation of nitrogen-doped holey carbon (NHC) with abundant in-plane holes derived from a rigid macrocycle cucurbit[6]uril self-assembly is reported. The NHC shows comparable activity, better stability and higher methanol tolerance towards the oxygen reduction reaction compared to the use of commercial Pt/C.

9.
Chemistry ; 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31688979

RESUMO

Interface engineering has been applied as an effective strategy to boost the electrocatalytic performance because of the strong coupling and synergistic effects between individual components. Here, we engineered vertically aligned FeOOH/CoO nanoneedle array with a synergistic interface between FeOOH and CoO on Ni foam (NF) by a simple impregnation method. The synthesized FeOOH/CoO exhibits outstanding electrocatalytic activity and stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. For the overall water splitting, the bifunctional FeOOH/CoO nanoneedle catalyst requires only a cell voltage of 1.58 V to achieve a current density of 10 mA cm-2 , which is much lower than that required for IrO2 //Pt/C (1.68 V). The FeOOH/CoO catalyst has been successfully applied for solar cell-driven water electrolysis, revealing its great potential for commercial hydrogen production and solar energy storage.

10.
Ecotoxicol Environ Saf ; 186: 109767, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31610358

RESUMO

Cadmium, a typical heavy metal, causes serious toxicities on many organs and tissues. As the last partially controlled class of polybrominated diphenyl ethers (PBDEs), BDE209 can also induce various health issues. Although apoptosis mediated by mitochondria has been known to be a key player in inducing toxicities by cadmium, the detailed mechanisms are incompletely understood. Moreover, co-existence of cadmium and PBDEs has been found in various environment context and human body. However, studies on the joint toxicity of cadmium and PBDEs are still limited with largely unknown mechanisms. In the present study, we investigated the adverse effects and mechanisms of single or combined treatment of CdCl2 and BDE209 on hepatocytes. We observed that apoptosis were significantly induced by CdCl2, and the combined treatment of CdCl2 and BDE209 greatly promoted the progression of apoptosis. BDE209 induced mild apoptosis. Mitochondria was the pivot of several mechanisms to induce apoptosis, including ROS production, decreased mitochondrial membrane potential (MMP), mtDNA damage and disordered calcium (Ca2+) homeostasis. However, we found that mtDNA damage and disordered Ca2+ homeostasis were the main mechanisms for CdCl2-induced apoptosis while ROS production played important roles in BDE209-induced apoptosis. Less mtDNA damage occurred in BDE209-treated cells. In the cells with combined treatment, CdCl2 and BDE209 exhibited a complementary pattern for the underlying mechanisms of apoptosis, leading to the joint toxicities, in which CdCl2 showed more contributions. In a conclusion, our results demonstrated that combined exposure to cadmium and BDE209 causes joint adverse effects on hepatocytes through diverse mechanisms as mediated by mitochondria.


Assuntos
Cádmio/toxicidade , Dano ao DNA , DNA Mitocondrial , Éteres Difenil Halogenados/toxicidade , Homeostase/efeitos dos fármacos , Apoptose/efeitos dos fármacos , Apoptose/genética , Sinergismo Farmacológico , Hepatócitos/efeitos dos fármacos , Hepatócitos/patologia , Homeostase/genética , Humanos , Potencial da Membrana Mitocondrial/efeitos dos fármacos
11.
Front Plant Sci ; 10: 1118, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31552080

RESUMO

Seed germination and formation are the beginning and ending, respectively, of a plant life cycle. These two processes are under fine regulation by the internal genetic information. Previously, we demonstrated that Arabidopsis MIDASIN 1 (MDN1) is required for ribosome biogenesis, and its dysfunction leads to pleiotropic developmental phenotypes, including impaired embryogenesis and slow seed germination. In this study, we further found that the weak mutant of MDN1, mdn1-1, exhibits an increased seed size phenotype. Seed proteomic analysis reveals that a number of proteins involved in seed development and response to external environments are mis-regulated by the MDN1 dysfunction. Many 2S seed storage proteins (SSPs) and late embryogenesis abundant (LEA) proteins are over-accumulated in the dry seeds of mdn1-1. Further, some genes encoding seed storage reserves are also upregulated in mdn1-1 seedlings. More interestingly, abscisic acid-insensitive 5 (ABI5) is over-accumulated in mdn1-1 seeds, and the loss of its function partially rescues the low seed germination rate of mdn1-1. Together, this study further demonstrates that MDN1 is essential for establishing a normal seed proteome, and its mutation triggers ABI5-mediated repression of seed germination.

12.
Nat Commun ; 10(1): 4163, 2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519871

RESUMO

Lifting the valley degeneracy of monolayer transition metal dichalcogenides (TMDs) would allow versatile control of the valley degree of freedom. We report a giant valley exciton splitting of 16 meV/T for monolayer WS2, using the proximity effect from an EuS substrate, which is enhanced by nearly two orders of magnitude from that obtained by an external magnetic field. More interestingly, a sign reversal of the valley splitting is observed as compared to that of WSe2 on EuS. Using first principles calculations, we investigate the complex behavior of exchange interactions between TMDs and EuS. The sign reversal is attributed to competing ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions for Eu- and S- terminated EuS surface sites. They act differently on the conduction and valence bands of WS2 compared to WSe2. Tuning the sign and magnitude of the valley exciton splitting offers opportunities for control of valley pseudospin for quantum information processing.

13.
J Colloid Interface Sci ; 557: 450-457, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31539841

RESUMO

Alloyed nanoparticles are promising electrocatalysts for electrochemical energy storage and conversion devices. However, syntheses of alloyed nanoparticles with controllable size and stoichiometry remain challenging. In this study, continuous, uniform and monodispersed bimetallic AgPd nanoparticles (NPs) with diameters ∼10 nm are achieved by electrochemical synthesis from quaternary ionic liquid microemulsion (ILM) for use as electrocatalysts for ethanol oxidation reaction (EOR). It is found that the ionic liquid, 1-butyl-3-methyl-imidazolium chloride ([BMIM]Cl), acts not only as a soft template and co-surfactant for the formation of micro-reactors, but also as an electrolyte for enhancing conductivity. The stoichiometry (AgxPdy), size and size distribution of AgPd NPs can be accurately tuned by varying electrolyte composition, electrodeposition conditions, and ionic liquids concentrations. Attributed to the high surface area, optimal stoichiometric ratio, and strong attachment onto substrates without using organic binders, the as-deposited AgxPdy NPs exhibit extraordinary electrocatalytic activity and stability for EOR. It is found that the mass activity of Ag49Pd51 NPs/Pt electrode reaches 3360 mA mg-1 for EOR in 1.0 M ethanol and 1.0 M KOH aqueous solution, which is much higher than commercial Pd/C catalyst (210.5 mA mg-1) and also the highest among state-of-the-art AgPd NPs electrocatalysts reported to date for EOR in alkaline media.

14.
Chem Commun (Camb) ; 55(81): 12184-12187, 2019 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-31544195

RESUMO

The energy-intensive nature, high level of CO2 emission and sophisticated infrastructure requirement hampered the utilization of the Haber-Bosch process as a green and decentralized system for NH3 production. The electrochemical N2 reduction reaction (NRR) provides a promising alternative to fix N2 under ambient conditions. Here, we report CoFe2O4 nanoclusters anchored on reduced graphene oxide for enhanced nitrogen reduction. In contrast to monometallic counterparts, this composite catalyst achieves a faradaic efficiency of 6.2% with a high rate of NH3 production of 4.2 × 10-11 mol s-1 cm-2 in 0.1 M Na2SO4 aqueous electrolyte. Amelioration of NRR performance could be attributed to the availability of different types of adsorption and active sites for N2 after the incorporation of Co in the Fe3O4 structure. Also, the homogeneous dispersion of nanoclusters on a 2D support can achieve higher active site density. This work provides a new category of binary metal oxides catalysts for NRR under ambient conditions.

15.
World J Gastroenterol ; 25(31): 4502-4511, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31496628

RESUMO

BACKGROUND: As one effective treatment for lateral pelvic lymph node (LPLN) metastasis (LPNM), laparoscopic LPLN dissection (LPND) is limited due to the complicated anatomy of the pelvic sidewall and various complications after surgery. With regard to improving the accuracy and completeness of LPND as well as safety, we tried an innovative method using indocyanine green (ICG) visualized with a near-infrared (NIR) camera system to guide the detection of LPLNs in patients with middle-low rectal cancer. AIM: To investigate whether ICG-enhanced NIR fluorescence-guided imaging is a better technique for LPND in patients with rectal cancer. METHODS: A total of 42 middle-low rectal cancer patients with clinical LPNM who underwent total mesorectal excision (TME) and LPND between October 2017 and March 2019 at our institution were assessed and divided into an ICG group and a non-ICG group. Clinical characteristics, operative outcomes, pathological outcomes, and postoperative complication information were compared and analysed between the two groups. RESULTS: Compared to the non-ICG group, the ICG group had significantly lower intraoperative blood loss (55.8 ± 37.5 mL vs 108.0 ± 52.7 mL, P = 0.003) and a significantly larger number of LPLNs harvested (11.5 ± 5.9 vs 7.1 ± 4.8, P = 0.017). The LPLNs of two patients in the non-IVG group were residual during LPND. In addition, no significant difference was found in terms of LPND, LPNM, operative time, conversion to laparotomy, preoperative complication, or hospital stay (P > 0.05). CONCLUSION: ICG-enhanced NIR fluorescence-guided imaging could be a feasible and convenient technique to guide LPND because it could bring specific advantages regarding the accuracy and completeness of surgery as well as safety.


Assuntos
Laparoscopia/métodos , Excisão de Linfonodo/métodos , Metástase Linfática/diagnóstico por imagem , Neoplasias Retais/cirurgia , Cirurgia Vídeoassistida/métodos , Idoso , Perda Sanguínea Cirúrgica/prevenção & controle , Perda Sanguínea Cirúrgica/estatística & dados numéricos , Feminino , Corantes Fluorescentes/administração & dosagem , Humanos , Verde de Indocianina/administração & dosagem , Laparoscopia/efeitos adversos , Laparoscopia/estatística & dados numéricos , Tempo de Internação/estatística & dados numéricos , Excisão de Linfonodo/efeitos adversos , Excisão de Linfonodo/estatística & dados numéricos , Linfonodos/diagnóstico por imagem , Linfonodos/patologia , Linfonodos/cirurgia , Metástase Linfática/patologia , Metástase Linfática/terapia , Masculino , Pessoa de Meia-Idade , Neoplasia Residual , Duração da Cirurgia , Imagem Óptica/métodos , Pelve , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/patologia , Estudos Retrospectivos , Resultado do Tratamento , Cirurgia Vídeoassistida/efeitos adversos , Cirurgia Vídeoassistida/estatística & dados numéricos
16.
Small ; : e1903397, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31496028

RESUMO

An unprecedented microwave-based strategy is developed to facilitate solid-phase, instantaneous delamination and decomposition of graphite fluoride (GF) into few-layer, partially fluorinated graphene. The shock reaction occurs (and completes in few seconds) under microwave irradiation upon exposing GF to either "microwave-induced plasma" generated in vacuum or "catalyst effect" caused by intense sparking of graphite at ambient conditions. A detailed analysis of the structural and compositional transformations in these processes indicates that the GF experiences considerable exfoliation and defluorination, during which sp2 -bonded carbon is partially recovered despite significant structural defects being introduced. The exfoliated fluorinated graphene shows excellent electrochemical performance as anode materials in potassium ion batteries and as catalysts for the conversion of O2 to H2 O2 . This simple and scalable method requires minimal energy input and does not involve the use of other chemicals, which is attractive for extensive research in fluorine-containing graphene and its derivatives in laboratories and industrial applications.

17.
Med Sci Monit ; 25: 6110-6119, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31415486

RESUMO

BACKGROUND Anti-angiogenic therapy has recently emerged as a highly promising therapeutic strategy for treating hepatocellular carcinoma (HCC). MATERIAL AND METHODS We assessed cellular proliferation, invasion, and activation of growth factors (VEGF and IL-8) with SDF-1 induced in the hepatocellular carcinoma cell line SMMC-7721, and this progression was limited by plumbagin (PL). The human umbilical vein endothelial cell line HUVEC was co-cultured with SDF-1-induced SMMC-7721, and the expressions of CXCR7, CXCR4, and PI3K/Akt pathways after PL treatment were detected by RT-PCR and Western blot analysis. RESULTS The treatment of the hepatoma cell line SMMC-7721 with SDF-1 resulted in enhanced secretion of the angiogenic factors, IL-8 and VEGF, and shows that these stimulatory effects are abolished by PL. The study further demonstrated that PL not only abolishes SDF-1-induced formation of endothelial tubes, but also inhibits expression of CXCR4 and CXCR7, and partially prevents activation of angiogenic signaling pathways. CONCLUSIONS The effect of PL on the SDF-1-CXCR4/CXCR7 axis has become an attractive target for inhibiting angiogenesis in hepatoma cells. Our results provide more evidence for the clinical application of PL as part of traditional Chinese medicine in modern cancer treatment.


Assuntos
Carcinoma Hepatocelular/patologia , Naftoquinonas/farmacologia , Neovascularização Patológica/metabolismo , Inibidores da Angiogênese/farmacologia , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Quimiocina CXCL12/metabolismo , Células Endoteliais da Veia Umbilical Humana , Humanos , Interleucina-8/metabolismo , Fígado/irrigação sanguínea , Neoplasias Hepáticas/metabolismo , Invasividade Neoplásica/patologia , Receptores CXCR/metabolismo , Receptores CXCR4/metabolismo , Transdução de Sinais/efeitos dos fármacos , Células Estromais/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo
18.
Talanta ; 205: 120092, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450435

RESUMO

VEGF mRNA, as an important biomarker for disease diagnosis and therapeutics, has received extensive attention. However, how to monitor its mRNA levels rapidly and sensitively remains a challenge. Herein, a strategy was designed for facile and efficient detection of VEGF mRNA and imaging in living cells using a collaborative system of a fluorophore-labeled single-stranded probe (P), reduced graphene oxide (rGO) and double-specific nuclease (DSN). The combination of strong fluorophore-quenching ability of rGO with DSN assisted signal amplification contributes to the superior sensitivity of the assay for VEGF mRNA, which was reflected by the lower limit of mRNA detection of 100 fM obtained using dual signal amplification manner. Furthermore, the developed sensor was directly used for intracellular mRNA imaging in vitro without the assistance of transfection reagent. In summary, the simple, ultra-sensitive and cost-effective mRNA assay system, which provided a general analysis strategy for other mRNAs assay by replacing the sequence of the probe, is hopeful for applying on the clinical diagnosis and therapy.


Assuntos
Grafite/química , Imagem Molecular/métodos , RNA Mensageiro/análise , Fator A de Crescimento do Endotélio Vascular/genética , Sistema Livre de Células , Sondas de DNA/química , Sondas de DNA/genética , DNA de Cadeia Simples/química , Corantes Fluorescentes/química , Células HeLa , Humanos , Imagem Molecular/instrumentação , Sensibilidade e Especificidade
19.
Adv Mater ; 31(40): e1901900, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31373051

RESUMO

For proton exchange membrane fuel cells (PEMFCs) to become a mainstream energy source, significant improvements in their performance, durability, and efficiency are necessary. To improve their durability, there must be a solid understanding of how the structural and electrochemical processes are affected during operation to propose mitigation strategies. To this aim, in situ and operando characterization techniques can locally identify structural and electrochemical processes, which cannot be captured using conventional techniques. Linking these properties in the same geometric area has been challenging due to its inherent limitations, such as sample size and imaging resolution. This has created a knowledge gap in structure-to-electrochemical performance relationships as operation and degradation unevenly affect different areas of the cell. In the recent past, catalyst layer degradation, hot spots, and water management have been structurally and electrochemically visualized in the same geometric area, revealing new interactions. To further the research in this direction, these interconnected fields are reviewed, followed by a roadmap for in situ characterization of PEMFCs, treating structural and electrochemical processes as a unified subject. With this approach, the knowledge of the degradation of PEMFCs will be significantly improved.

20.
Chemphyschem ; 20(22): 2936-2945, 2019 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-31264336

RESUMO

Electrochemical water splitting by renewable energy resources is an efficient and green approach for hydrogen gas production. However, the anodic oxygen evolution reaction (OER) largely impedes the industrial application due to its sluggish four-electron-transition kinetics. Although various materials have been developed to accelerate the OER rate, still some issues should be addressed to meet the industrial demand: (i) considerable 200-300 mV overpotential as extra onset energy input, (ii) limited survival and performance in acidic electrolyte for the majority of oxide/hydroxide composite materials, (iii) unsatisfying long-term durability and (iv) the need for facile and scalable preparation methods. Here, we emphasize on multi-metallic composites with enhanced OER activity based on both precious and nonprecious elements that outperform the unary and binary composites. The regulation effect from multi-metal incorporation is also summarized systematically: (i) introducing foreign metal atoms to the host material boosts the physical properties such as conductivity, surface area, defect density, morphology, wettability, etc., (ii) metal doping can synergistically regulate the electronic features of the host material, e. g. oxygen vacancy, eg orbit filling, coordinative number and covalence state, which can optimize the absorption/desorption energy of the M-O intermediate, (iii) chaotic impact from the added atoms twists the catalyst lattice into a more aggressive and higher energy state, which is more feasible to transform to an active intermediate with lower required energy supply. This review aims to provide a practical approach to further improve the OER performance via multi-metallic-based catalysts.

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