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1.
J Am Chem Soc ; 142(28): 12430-12439, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32530616

RESUMO

Photocatalytic nitrogen fixation represents a green alternative to the conventional Haber-Bosch process in the conversion of nitrogen to ammonia. In this study, a series of Bi5O7Br nanostructures were synthesized via a facile, low-temperature thermal treatment procedure, and their photocatalytic activity toward nitrogen fixation was evaluated and compared. Spectroscopic measurements showed that the tubular Bi5O7Br sample prepared at 40 °C (Bi5O7Br-40) exhibited the highest electron-transfer rate among the series, producing a large number of O2.- radicals and oxygen vacancies under visible-light photoirradiation and reaching a rate of photocatalytic nitrogen fixation of 12.72 mM·g-1·h-1 after 30 min of photoirradiation. The reaction dynamics was also monitored by in situ infrared measurements with a synchrotron radiation light source, where the transient difference between signals in the dark and under photoirradiation was analyzed and the reaction pathway of nitrogen fixation was identified. This was further supported by results from density functional theory calculations. The reaction energy of nitrogen fixation was quantitatively estimated and compared by building oxygen-enriched and anoxic models, where the change in the oxygen vacancy concentration was found to play a critical role in determining the nitrogen fixation performance. Results from this study suggest that Bi5O7Br with rich oxygen vacancies can be used as a high-performance photocatalyst for nitrogen fixation.

2.
Nanoscale ; 12(23): 12196-12209, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32501466

RESUMO

The photocatalytic conversion of green-house gas CO2 into high value-added carbonaceous fuels and chemicals through harvesting solar energy is a great promising strategy for simultaneously tackling global environmental issues and the energy crisis. Considering the vital role of active sites in determining the activity and selectivity in photocatalytic CO2 reduction reactions, great efforts have been directed toward engineering active sites for fabricating efficient photocatalysts. This review highlights recent advances in the strategies for engineering active sites on surfaces and in open frameworks toward photocatalytic CO2 reduction, referring to surface vacancies, doped heteroatoms, functional groups, loaded metal nanoparticles, crystal facets, heterogeneous/homogeneous single-site catalysts and metal nodes/organic linkers in metal organic frameworks.

3.
Cell Mol Life Sci ; 2020 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32318758

RESUMO

Faithful chromosome segregation during mitosis requires the correct assembly of kinetochore on the centromere. CENP-A is a variant of histone H3, which specializes the centromere region on chromatin and mediates the kinetochore assembly. The Mis18 complex plays a critical role in initiating the centromere loading of the newly-synthesized CENP-A. However, it remains unclear how Mis18 complex (spMis18, spMis16 and spMis19) is located to the centromere to license the recruitment of Cnp1CENP-A in Schizosaccharomyces pombe. We found that spMis18 directly binds to nucleosomal DNA through its extreme C-terminus and interacts with H2A-H2B dimer via the acidic region on the surface of its Yippee-like domain. Live-cell imaging confirmed that mutation of the acidic region and deletion of the extreme C-terminus significantly impairs the localization of spMis18 and Cnp1 to the centromere and delays chromosome segregation during mitosis. Our findings illustrate that the interaction of spMis18 with histone H2A-H2B and DNA plays important roles in the recruitment of spMis18 and Cnp1 to the centromere in fission yeast.

4.
Zhongguo Zhong Yao Za Zhi ; 45(6): 1311-1315, 2020 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-32281341

RESUMO

Pinellia ternata is a medicinal herb of Araceae, and its tubers are used as medicines. It is a common Chinese herbal medicine in China and has a large market demand. When exposing to strong light intensity and high temperature during the growth process, P. ternata withers in a phenomenon known as "sprout tumble", which largely limits tuber production. Shade can effectively delay sprout tumble formation and increase its yield, however the relevant regulation mechanism is unclear. DNA methylation, as a self-modifying response to environmental changes, is often involved in the regulation of plant growth and development. In this study, P. ternata grown under natural light and 90% shading were selected as the control group and the experimental group for genomic DNA methylation analysis by using methylate sensitive amplification polymorphism(MSAP). The results showed that a total of 617 loci were detected with 20 pairs of primers, of which 311 were in the natural light group and 306 in the shading group. The methylation sites in the light and shading groups accounted for 58.2% and 71.57%, respectively, and the methylation ratios in the methylation sites were 27.65% and 29.41%, respectively, indicating that shading significantly induced the genome DNA methylation of P. ternata. Compared to the natural light group, shading promoted 32.51% of the genes methylation, while inducing 16.25% gene demethylation. This study reveals the DNA methylation variation of P. ternata under shading conditions, which lays a preliminary theoretical foundation for further analysis of the mechanism of shading regulation of P. ternata growth from epigenetic level.


Assuntos
Metilação de DNA , Escuridão , Pinellia/genética , Pinellia/efeitos da radiação , Luz Solar , China , Epigênese Genética , Plantas Medicinais/genética , Plantas Medicinais/efeitos da radiação
5.
Zhongguo Zhong Yao Za Zhi ; 45(2): 341-346, 2020 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-32237316

RESUMO

Pinellia ternata belongs to the Araceae family and is a medicinal herb. The tuber is the medicinal organ with antitussive, antiemetic and anti-tumor activities. It is easy to encounter high temperature environment during the growth periods, leading to decrease of tuber production. At present, the mechanism of response to high temperature stress in P. ternata is still unknown. DNA methylation plays a vital role in plant protection against adversity stress as a way of epigenetic regulation. In this study, P. ternata was used as material for treatment of high temperature stress at 0 h, 6 h and 80 h, and methylation sensitive amplification polymorphism(MSAP) analysis was conducted on the changes of DNA methylation in its genome. The results showed that 20 pairs of MSAP primers were selected from 100 MSAP primers with multiple clear and uniform bands, and 353, 355 and 342 loci were amplified from materials of P. ternata treated in the high temperature stress 0 h, 6 h and 80 h, respectively. Cytosine methylation levels of CCGG context in the above materials were characterized as 60.91%, 44.79% and 44.74%, respectively. And the full methylation ratios were 16.71%, 22.25% and 29.24, respectively. It demonstrated that high temperature stress significantly induced the down-regulation of DNA methylation level and up-regulation of the full methylation rate in P. ternata genome. This study provides a preliminary theoretical reference for analyzing the mechanism of P. ternata responding to high temperature stress from the epigenetic perspective.


Assuntos
Metilação de DNA , Epigênese Genética , Temperatura Alta , Pinellia/genética , Plantas Medicinais/genética
6.
Chem Rev ; 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32186373

RESUMO

Single-atom photocatalysts have shown their compelling potential and arguably become the most active research direction in photocatalysis due to their fascinating strengths in enhancing light-harvesting, charge transfer dynamics, and surface reactions of a photocatalytic system. While numerous comprehensions about the single-atom photocatalysts have recently been amassed, advanced characterization techniques and vital theoretical studies are strengthening our understanding on these fascinating materials, allowing us to forecast their working mechanisms and applications in photocatalysis. In this review, we begin by describing the general background and definition of the single-atom photocatalysts. A brief discussion of the metal-support interactions on the single-atom photocatalysts is then provided. Thereafter, the current available characterization techniques for single-atom photocatalysts are summarized. After having some fundamental understanding on the single-atom photocatalysts, their advantages and applications in photocatalysis are discussed. Finally, we end this review with a look into the remaining challenges and future perspectives of single-atom photocatalysts. We anticipate that this review will provide some inspiration for the future discovery of the single-atom photocatalysts, manifestly stimulating the development in this emerging research area.

7.
J Am Chem Soc ; 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32130002

RESUMO

Harvesting solar energy for catalytic conversion of CO2 into valuable chemical fuels/feedstocks is an attractive yet challenging strategy to realize a sustainable carbon-cycle utilization. Homogeneous catalysts typically exhibit higher activity and selectivity as compared with heterogeneous counterparts, benefiting from their atomically dispersed catalytic sites and versatile coordination structures. However, it is still a "black box" how the coordination and electronic structures of catalysts dynamically evolve during the reaction, forming the bottleneck for understanding their reaction pathways. Herein, we demonstrate to track the mechanistic pathway of photocatalytic CO2 reduction using a terpyridine nickel(II) complex as a catalyst model. Integrated with a typical homogeneous photosensitizer, the catalytic system offers a high selectivity of 99% for CO2-to-CO conversion with turnover number and turnover frequency as high as 2.36 × 107 and 385.6 s-1, respectively. We employ operando and time-resolved X-ray absorption spectroscopy, in combination with other in situ spectroscopic techniques and theoretical computations, to track the intermediate species of Ni catalyst in the photocatalytic CO2 reduction reaction for the first time. Taken together with the charge dynamics resolved by optical transient absorption spectroscopy, the investigation elucidates the full mechanistic reaction pathway including some key factors that have been often overlooked. This work opens the "black box" for CO2 reduction in the system of homogeneous catalysts and provides key information for developing efficient catalysts toward artificial photosynthesis.

8.
J Phys Chem Lett ; : 1746-1752, 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-32048849

RESUMO

Recent years have witnessed various in-depth research efforts on self-reconstruction behavior toward electrocatalysis. Tracking the phase transformation and evolution of true active sites is of great significance for the development of self-reconstructed electrocatalysts. Here, the optimized atomic sulfur-doped bismuth nanobelt (S-Bi) is fabricated via an electrochemical self-reconstruction evolved from Bi2S3. Advanced technologies have demonstrated that the nonmetallic S atoms have been doped into the lattice Bi frame, leading to the reconstruction of local electronic structure of Bi. The as-prepared S-Bi nanobelt exhibits a remarkable NH3 generation rate of 10.28 µg h-1 mg-1 and Faradaic efficiency of 10.48%. Density functional theory calculations prove that the S doping can significantly lower the energy barrier of the rate-determining step and enlarge the N≡N bond for further dissociation toward N2 fixation. This work not only establishes insights into the evolution process of electrochemically derived self-reconstruction but also unravels the root of the N2 reduction reaction mechanism associated with the atomic nonmetal dopants.

9.
Artigo em Inglês | MEDLINE | ID: mdl-31922641

RESUMO

Single-atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single-atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single-atom Pt/C3 N4 catalyst in photocatalytic water splitting by synchronous illumination X-ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt-N bond cleavage to form a Pt0 species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum-decorated C3 N4 catalyst. As expected, H2 production activity (14.7 mmol h-1 g-1 ) was enhanced significantly with the single-atom Pt/C3 N4 catalyst as compared to metallic Pt-C3 N4 (0.74 mmol h-1 g-1 ).

10.
Chem Sci ; 10(31): 7310-7326, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31768231

RESUMO

Heterogeneous thermocatalytic and electrocatalytic conversion of CO x including CO and CO2 to value-added products, which can be performed through three promising approaches - syngas conversion, CO2 hydrogenation and CO2 electroreduction, are highly important to achieving a carbon-neutral cycle associated with the continuing consumption of fossil fuels. Toward the formation of value-added C2+ products, precise regulation of C-C coupling requires rational design of catalysts in all the three approaches, which usually share similar fundamentals from the viewpoint of surface science. In this article, we outline the recent advances in catalyst design for controlling C-C coupling in syngas conversion, CO2 hydrogenation and CO2 electroreduction from the viewpoint of surface science. Specifically, the fundamental insights are provided for each conversion approach, which makes a connection between thermocatalysis and electrocatalysis in terms of catalytic site design. Finally, the challenges and opportunities are discussed in the hope of inspiring new ideas to achieve more efficient C-C coupling in thermocatalytic and electrocatalytic CO x conversion.

11.
Small ; 15(28): e1901020, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31148404

RESUMO

Oxygen evolution reaction (OER) is of great significance for hydrogen production via water electrolysis, which, however, demands development of highly active, durable, and cost-effective electrocatalysts in order to stride into a renewable energy era. Herein, highly efficient and long-term durable OER by coupling B and P into an amorphous porous NiFe-based electrocatalyst is reported, which possesses an amorphous porous metallic bulk structure and high corrosion resistance, and overcomes the issues associated with currently used catalyst nanomaterials. The PB codoping in the activated NiFePB (a-NiFePB) delocalizes both Fe and Ni at Fermi energy level and enhances p-d hybridization as simulated by density functional theory calculations. The harmonized electronic structure and unique porous framework of the a-NiFePB consequently improve the OER activity. The activated NiFePB thus exhibits an extraordinarily low overpotential of 197 mV for harvesting 10 mA cm-2 OER current density and 233 mV for reaching 100 mA cm-2 under chronopotentiometry condition, with the Tafel slope harmoniously conforming to 34 mV dec-1 . Impressive long-term stability of this new catalyst is evidenced by only limited activity decay after 1400 h operation at 100 mA cm-2 . This work strategically directs a way for heading up a promising energy conversion alternative.

12.
Nanoscale ; 11(23): 11064-11070, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31166355

RESUMO

Photocatalytic conversion of CO2 into carbonaceous chemical fuels and building blocks is an intriguing strategy for solving fossil energy crisis and reducing CO2 emission. Recently, development of atomically dispersed catalytic sites for photocatalytic CO2 reduction has sparked tremendous interest as their coordinatively unsaturated states, tunable electronic structures and well-defined active sites provide versatile knobs for tuning CO2 conversion. While this Minireview mainly highlights recent key developments in this important research field and elucidates the common fundamentals behind various materials systems, it also provides insights into the future development and emphasizes opportunities and challenges.

13.
J Am Chem Soc ; 141(27): 10924-10929, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31200598

RESUMO

Photoelectrochemical (PEC) reduction of CO2 into chemical fuels and chemical building blocks is a promising strategy for addressing the energy and environmental challenges, which relies on the development of p-type photocathodes. Cu2O is such a p-type semiconductor for photocathodes but commonly suffers from detrimental photocorrosion and chemical changes. In this communication, we develop a facile procedure for coating a metal-organic framework (MOF) on the surface of a Cu2O photocathode, which can both prevent photocorrosion and offer active sites for CO2 reduction. As evidenced by ultrafast spectroscopy, the formed interface can effectively promote charge separation and transfer. As a result, both the activity and durability of Cu2O are dramatically enhanced for PEC CO2 reduction. This work provides fresh insights into the design of advanced hybrid photoelectrodes and highlights the important role of interfacial charge dynamics in PEC CO2 conversion.

14.
J Am Chem Soc ; 141(19): 7807-7814, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-31038309

RESUMO

Nitrogen fixation in a simulated natural environment (i.e., near ambient pressure, room temperature, pure water, and incident light) would provide a desirable approach to future nitrogen conversion. As the N≡N triple bond has a thermodynamically high cleavage energy, nitrogen reduction under such mild conditions typically undergoes associative alternating or distal pathways rather than following a dissociative mechanism. Here, we report that surface plasmon can supply sufficient energy to activate N2 through a dissociative mechanism in the presence of water and incident light, as evidenced by in situ synchrotron radiation-based infrared spectroscopy and near ambient pressure X-ray photoelectron spectroscopy. Theoretical simulation indicates that the electric field enhanced by surface plasmon, together with plasmonic hot electrons and interfacial hybridization, may play a critical role in N≡N dissociation. Specifically, AuRu core-antenna nanostructures with broadened light adsorption cross section and active sites achieve an ammonia production rate of 101.4 µmol g-1 h-1 without any sacrificial agent at room temperature and 2 atm pressure. This work highlights the significance of surface plasmon to activation of inert molecules, serving as a promising platform for developing novel catalytic systems.

15.
Nat Commun ; 10(1): 1779, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30992441

RESUMO

It is highly profitable to transform glycerol - the main by-product from biodiesel production to high value-added chemicals. In this work, we develop a photoelectrochemical system based on nanoporous BiVO4 for selective oxidation of glycerol to 1,3-dihydroxyacetone - one of the most valuable derivatives of glycerol. Under AM 1.5G front illumination (100 mW cm-2) in an acidic medium (pH = 2) without adscititious oxidant, the nanoporous BiVO4 photoanode achieves a glycerol oxidation photocurrent density of 3.7 mA cm-2 at a potential of 1.2 V versus RHE with 51% 1,3-dihydroxyacetone selectivity, equivalent to a production rate of 200 mmol of 1,3-dihydroxyacetone per m2 of illumination area in one hour.

16.
Adv Mater ; 30(48): e1806572, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30488500
17.
J Am Chem Soc ; 140(48): 16514-16520, 2018 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-30407807

RESUMO

Development of visible-light photocatalytic materials is an ultimate goal for solar-driven CO2 conversion. Au nanoclusters (NCs) may potentially serve as components for harvesting visible light but can hardly perform solar-driven CO2 reduction due to the lack of catalytic sites. Herein, we report an effective strategy for turning Au nanoclusters catalytically active for visible-light CO2 reduction, in which metal cations (Fe2+, Co2+, Ni2+, and Cu2+) are grafted to the Au NCs using l-cysteine as a bridging ligand. The metal-S bonding bridge facilitates the electron transfer from Au NCs to metal cations so that the grafted metal cations can receive photoinduced electrons and work as catalytic sites for CO2 reduction. The varied d-band centers and binding energies with CO2 for different metal cations allow tuning electron transfer efficiency and CO2 activation energy. Furthermore, the photostability of Au NCs-based catalyst can be significantly enhanced through the encapsulation with metal-organic frameworks. This work opens a new door for the photocatalyst design based on metal clusters and sheds light on the surface engineering of metal clusters toward specific applications.

18.
Angew Chem Int Ed Engl ; 57(50): 16447-16451, 2018 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-30350910

RESUMO

Quantum dots (QDs), a class of promising candidates for harvesting visible light, generally exhibit low activity and selectivity towards photocatalytic CO2 reduction. Functionalizing QDs with metal complexes (or metal cations through ligands) is a widely used strategy for improving their catalytic activity; however, the resulting systems still suffer from low selectivity and stability in CO2 reduction. Herein, we report that doping CdS QDs with transition-metal sites can overcome these limitations and provide a system that enables highly selective photocatalytic reactions of CO2 with H2 O (100 % selectivity to CO and CH4 ), with excellent durability over 60 h. Doping Ni sites into the CdS lattice leads to effective trapping of photoexcited electrons at surface catalytic sites and substantial suppression of H2 evolution. The method reported here can be extended to various transition-metal sites, and offers new opportunities for exploring QD-based earth-abundant photocatalysts.

19.
Dalton Trans ; 47(35): 12035-12040, 2018 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-30101959

RESUMO

Surface and interface structures are considered as the critical parameters which can be engineered to improve the performance of catalysts. This Frontiers article highlights our recent advances in surface and interface design toward photocatalytic water splitting.

20.
Chemistry ; 24(69): 18398-18402, 2018 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-30102805

RESUMO

Metal-containing nanocrystals with well-designed surface structures represent a class of model systems for revealing the fundamental physical and chemical processes involved in heterogeneous catalysis. Herein it is shown how surface modification can be utilized as an efficient strategy for controlling the surface electronic state of catalysts and, thus, for tuning their catalytic activity. As model catalysts, the Pd-tetrahedron-TiO2 nanostructures, modified on the surface with different foreign atoms, showed a varied activity in the catalytic decomposition of formic acid towards H2 production. The catalytic activity increases with a reduction in the work function of modified atoms; this reduction can be well explained by a surface polarization mechanism. In this hybrid system, the difference in the work functions of Pd and modified atoms results in surface polarization on the Pd surface and, thus, in the tuning of its charge state. Together with the Schottky junction between TiO2 and metals, the tuned charge state enables the promotion of catalytic efficiency in the catalytic decomposition of formic acid to H2 and CO2 .

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