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1.
Artigo em Inglês | MEDLINE | ID: mdl-32181944

RESUMO

Hierarchical supramolecular chiral liquid-crystalline polymer assemblies are highly challenging to construct in situ in a controlled manner. Here, we report polymerization-induced chiral self-assembly (PICSA) for the first time, by which hierarchical supramolecular chiral azobenzene-containing block copolymer (Azo-BCP) assemblies were constructed in a controlled manner, not only for different morphologies but also for chiroptical properties, with π-π stacking interactions occurring in the layered structure of Azo smectic phases. The evolution of chirality from terminal alkyl chain to Azo mesogen building blocks and further induction of supramolecular chirality in BCP liquid-crystalline assemblies during PICSA process is achieved. A full spectrum of morphologies spanning spheres, worms, helical fibers, lamellae and vesicles were observed and the morphological transition had a crucial effect on the chiral expression of Azo-BCP assemblies. The supramolecular chirality of Azo-BCP assemblies destroyed by 365 nm UV light irradiation can be fully recovered by heating-cooling treatment and this dynamic reversible achiral-chiral switch can be repeated at least five times. The PICSA process provides a novel platform for effectively producing photoresponsive hierarchical supramolecular chiral polymer assemblies in situ with various morphologies in a well-controlled manner.

2.
Adv Mater ; : e1907112, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32020715

RESUMO

Electrochemical conversion of nitrogen (N2 ) into value-added ammonia (NH3 ) is highly desirable yet formidably challenging due to the extreme inertness of the N2 molecule, which makes the development of a robust electrocatalyst prerequisite. Herein, a new class of bullet-like M-Te (M = Ru, Rh, Ir) glassy porous nanorods (PNRs) is reported as excellent electrocatalysts for N2 reduction reaction (NRR). The optimized IrTe4 PNRs present superior activity with the highest NH3 yield rate (51.1 µg h-1 mg-1 cat. ) and Faraday efficiency (15.3%), as well as long-term stability of up to 20 consecutive cycles, making them among the most active NRR electrocatalysts reported to date. Both the N2 temperature-programmed desorption and valence band X-ray photoelectron spectroscopy data show that the strong chemical adsorption of N2 is the key for enhancing the NRR and suppressing the hydrogen evolution reaction of IrTe4 PNRs. Density functional theory calculations comprehensively identify that the superior adsorption strength of IrTe4 adsorptions originates from the synergistic collaboration between electron-rich Ir and the highly electroactive surrounding Te atoms. The optimal adsorption of both N2 and H2 O in alkaline media guarantees the superior consecutive NRR process. This work opens a new avenue for designing high-performance NRR electrocatalysts based on glassy materials.

3.
Nano Lett ; 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-32052980

RESUMO

Spin engineering provides a powerful strategy for manipulating the interaction between electrons in the d orbital and oxygen-containing adsorbates, while a little endeavor was performed to understand whether such a strategy can make a prosperous enhancement for fuel electrooxidations. Herein, we demonstrate that spin engineering of trimetallic Pd-Fe-Pt nanomeshes (NMs) can achieve superior enhancement for fuel electrooxidations. Magnetization characterizations reveal that Pd59Fe27Pt14 NMs own the highest number of polarized spins (µb = 0.85 µB/f.u.), playing an important role on facilitating the adsorption of OHads to promote the oxidation of COads, as confirmed by theoretical results. Consequently, the optimized Pd59Fe27Pt14 NMs exhibit excellent methanol oxidation reaction activity and stability with a mass activity of 1.61 A mgPt-1, 2.6-fold and 7.3-fold larger than those of PtRu/C and Pt/C. Such catalysts also present exceptional performances in ethanol oxidation and formic acid oxidation reactions. Our work highlights a new strategy for designing efficient electrocatalysts for fuel electrooxidations and beyond.

4.
Phys Chem Chem Phys ; 21(46): 25535-25547, 2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31738352

RESUMO

In this perspective, we review two new strategies for computational design and discovery of two-dimensional (2D) transition-metal (TM) free electro-catalysts for the oxygen reduction reaction (ORR) and the nitrogen reduction reaction (NRR). The "2D binary compound" strategy for designing ORR electro-catalysts shows promising applications, which benefits from abundant intrinsic catalytic sites for the adsorption of reaction intermediates. And with the "activated B site" strategy for designing NRR electro-catalysts, several novel NRR electro-catalysts with extremely low limiting potential are developed. Computational-simulation-driven material design from a bottom-up method could not only provide rational strategies, but also accelerate the discovery of novel materials.

5.
Genes (Basel) ; 10(11)2019 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-31739562

RESUMO

Leaves are one of the most important organs of plants, and yet, the association between leaf color and consumable traits remains largely unclear. Tea leaves are an ideal study system with which to investigate the mechanism of how leaf coloration affects palatability, since tea is made from the leaves of the crop Camellia sinensis. Our genomic resequencing analysis of a tea cultivar ZiJuan (ZJ) with purple leaves and altered flavor revealed genetic variants when compared with the green-leaf, wild type cultivar YunKang(YK). RNA-Seq based transcriptomic comparisons of the bud and two youngest leaves in ZJ and YK identified 93%, 9% and 5% expressed genes that were shared in YK- and ZJ-specific cultivars, respectively. A comparison of both transcript abundance and particular metabolites revealed that the high expression of gene UFGT for anthocyanin biosynthesis is responsible for purple coloration, which competes with the intermediates for catechin-like flavanol biosynthesis. Genes with differential expression are enriched in response to stress, heat and defense, and are casually correlated with the environmental stress of ZJ plant origin in the Himalayas. In addition, the highly expressed C4H and LDOX genes for synthesizing flavanol precursors, ZJ-specific CLH1 for degrading chlorophyll, alternatively spliced C4H and FDR and low photosynthesis also contributed to the altered color and flavor of ZJ. Thus, our study provides a better molecular understanding of the effect of purple coloration on leaf flavor, and helps to guide future engineering improvement of palatability.

6.
Theranostics ; 9(26): 8266-8276, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31754395

RESUMO

Rationale: Despite the promises of applying theranostic nanoagents for imaging-guided cancer therapy, the chronic retention of these nanoagents may cause safety concerns that hinder their future clinical applications. The metabolizable nanoagents with rapid renal excretion to avoid long-term toxicity is a possible solution for this issue. Method: Herein, we synthesize ultra-small metal-organic coordination polymer nanodots based on ruthenium ion (Ru3+) / phenanthroline (Phen) (Ru-Phen CPNs) with superior near-infrared (NIR) absorption. The size, photothermal conversion, cytotoxicity, photoacoustic imaging, in vivo & in vitro cancer treatment efficiency and biosafety are tested. Results: The size of the ultra-small Ru-Phen CPNs is 6.5 nm. The photothermal conversion efficiency is measured to be ~ 60.69 %, much higher than that of previously reported photothermal agents. The Ru-Phen CPNs could be employed for photoacoustic (PA, 808 nm) imaging-guided photothermal therapy (PTT, 808 nm, 0.5 W/cm2) with great performance. Notably, the intrinsic PA signals (808 nm) of Ru-Phen CPNs are observed in kidneys of treated mice, illustrating efficient renal clearance of those ultra-small CPNs. Moreover, the clearance of CPNs is further confirmed by detecting Ru levels in urine and feces. Conclusion: Our work presents a new type of ultra-small Ru-based CPNs with a record high photothermal conversion efficiency, efficient tumor retention after systemic administration, and rapid renal excretion to avoid long-term toxicity, promising for imaging-guided photothermal therapy.

7.
Phys Chem Chem Phys ; 21(42): 23441-23446, 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31616881

RESUMO

Two-dimensional (2D) materials are expected to be utilized as electrodes for alkali metal ion batteries due to their exceptional properties, but the larger size of K ions has been supposed to induce structural collapses and low charge-discharge efficiency. In this work, we propose transition metal dichalcogenide (TMD) materials as the anode electrodes for potassium ion batteries (PIBs). K ions can stably be adsorbed on most of the TMD materials with strong adsorption energies, and the structural phase transition from the 2H phase to the 1T phase can further enhance the K adsorption. It is surprising that, the diffusion barriers for K ions on TMD monolayers are low enough (less than 0.05 eV) to allow K ions to freely migrate. Among the TMD materials that we consider here, both VS2 and TiS2 exhibit extraordinary properties with good electronic conductivity, fast K diffusion, optimal open circuit voltage and high theoretical K storage capacity, which are promising anode materials for K ion batteries.

8.
Chem Asian J ; 14(23): 4296-4302, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31617314

RESUMO

A triphenylamine derivative decorated with an azobenzene group (TDA) was synthesized via a SuFEx click reaction and its polymer, poly(triphenylamine) (PTDA), was polymerized through a redox polymerization. More interestingly, its polymeric metal complex, PTDA-Fe, can be simply obtained via one-pot reaction between TDA and FeCl3 owing to TDA showing a strong affinity to the FeIII ion. The sandwich memory device based on PTDA nanofilms as active layers exhibited a binary memory performance. However, the memory device based on its polymeric metal complex exhibited a unique ternary memory behavior. The different memory performances should come from the different conductive mechanism. The mechanism of such ternary memory devices is illustrated based on both the theoretical calculation and experiments. Our work provides new insights into the preparation of novel materials for multilevel memory devices.

9.
ACS Appl Mater Interfaces ; 11(45): 42014-42020, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31597428

RESUMO

Exploring highly efficient catalysts for the electrochemical hydrogen evolution reaction (HER) is highly demanded in the sustainable production of hydrogen. MoS2 is recognized as a potential candidate catalyst for HER, but its active site is mainly located at the edges, which is extremely limited. Here, we have investigated the catalytic performance of HER in the MoS2 basal planes during the structural transition from the 2H to the 1T' phase. Different kinds of 2H/1T' structural interfaces are considered, and the adsorbed H free energies (ΔGH) on these surfaces were calculated. The active site for H adsorption is on the top of S atoms at the 2H/1T' phase boundary. The zigzag 2H/1T' interfaces exhibit an optimal performance for the Volmer reaction with the ΔGH being very close to zero. The Volmer-Heyrovsky reaction is dominantly preferred to the Volmer-Tafel reaction. Our study provides a new picture to boost up the active sites of the basal plane for HER on MoS2, and this electrocatalytic mechanism is also applicable for other transition metal dichalcogenide materials.

10.
Angew Chem Int Ed Engl ; 58(47): 16820-16825, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31535447

RESUMO

The electrocatalytic urea oxidation reaction (UOR) provides more economic electrons than water oxidation for various renewable energy-related systems owing to its lower thermodynamic barriers. However, it is limited by sluggish reaction kinetics, especially by CO2 desorption steps, masking its energetic advantage compared with water oxidation. Now, a lattice-oxygen-involved UOR mechanism on Ni4+ active sites is reported that has significantly faster reaction kinetics than the conventional UOR mechanisms. Combined DFT, 18 O isotope-labeling mass spectrometry, and in situ IR spectroscopy show that lattice oxygen is directly involved in transforming *CO to CO2 and accelerating the UOR rate. The resultant Ni4+ catalyst on a glassy carbon electrode exhibits a high current density (264 mA cm-2 at 1.6 V versus RHE), outperforming the state-of-the-art catalysts, and the turnover frequency of Ni4+ active sites towards UOR is 5 times higher than that of Ni3+ active sites.

11.
Inorg Chem ; 58(18): 12415-12421, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31483642

RESUMO

Many strategies to optimize molybdenum selenide based electrocatalysts for hydrogen evolution reaction (HER) have been explored; however, the modulation of molybdenum selenide on the molecular scale remains an ongoing challenge. Here, we synthesized a new molecular HER electrocatalyst based on a molybdenum-selenium cluster (Mo3Se13) and further realized its modulation by precise sulfur substitution at the molecular level to enhance the HER activity. The density functional theory (DFT) calculations demonstrated that the substituted sulfur could promote the hydrogen adsorption process and thus improve the HER performance. This work not only realizes the selective replacement of the bridging selenium atom with a sulfur atom in the molybdenum-selenium cluster for the first time but also provides a precise model for illustrating the structure-property relationship in electrocatalysis on the molecular level.

12.
ACS Nano ; 13(10): 11303-11309, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31532626

RESUMO

Although the water gas shift (WGS) reaction has sparked intensive attention for the production of high-purity hydrogen, the design of cost-efficient catalysts with noble metal-like performance still remains a great challenge. Here, we successfully overcome this obstacle by using Se-incorporated MoS2 with a 1T phase. Combining the optimized electronic structure, additional active sites from edge sites, and a sulfur vacancy based on the 1T phase, as well as the high surface ratio from the highly open structure, the optimal MoS1.75Se0.25 exhibits superior activity and stability compared to the conventional 2H-phase MoS2, with poor activity, large sulfur loss, and rapid inactivation. The hydrogen production of MoS1.75Se0.25 is 942 µmol, which is 1.9 times higher than MoS2 (504 µmol) and 2.8 times higher than MoSe2 (337 µmol). Furthermore, due to the lattice stabilization via Se-incorporation, MoS1.75Se0.25 exhibited excellent long-term stability without obvious change in more than 10 reaction rounds. Our results demonstrate a pathway to design efficient and cost-efficient catalysts for WGS.

13.
ACS Nano ; 13(9): 9936-9943, 2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31381315

RESUMO

Controlling the spin of metal atoms embedded in molecular systems is a key step toward the realization of molecular electronics and spintronics. Many efforts have been devoted to explore the influencing factors dictating the survival or quenching of a magnetic moment in a metal-organic molecule, and among others, the spin control by axial ligand attachments is the most promising. Herein, from the interplay of high-resolution scanning tunneling microscopy imaging/manipulation and scanning tunneling spectroscopy measurements together with density functional theory calculations, we successfully demonstrate that a Ni trimer within a metal-organic motif acquires a net spin promoted by the adsorption of an on-top Br atom. The spin localization in the trimetal centers bonded to Br was monitored via the Kondo effect. The removal of the Br ligand resulted in the switch from a Kondo ON to a Kondo OFF state. The magnetic state induced by the Br ligand is theoretically attributed to the enhanced Br 4pz and Ni 3dz2 states due to the charge redistribution. The manipulation strategy reported here provides the possibility to explore potential applications of spin-tunable structures in spintronic devices.

14.
Nanotechnology ; 30(46): 465202, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31422944

RESUMO

Currently, identifying suitable oxygen reduction reaction (ORR) catalysts in novel two-dimensional (2D) materials has attracted more and more research attention. Here, we have studied the catalytic activities of 2D h-BeN2 and MgN2 monolayers for ORR by using first-principles calculations. The calculated results reveal that the direct quasiparticle bandgap of BeN2 monolayer is 3.32 eV, and the indirect bandgap of MgN2 is 3.42 eV. 2D h-BeN2 and MgN2 exhibit high exciton binding energies of 1.07 and 0.83 eV respectively, and their optical properties are determined by bound exciton transitions due to the strong quantum confinement effects. Importantly, h-BeN2 and MgN2 monolayers with positive-charged (+1.6 e) metal atom (Be/Mg) on the surface exhibit excellent adsorption ability for O2 and ORR intermediates, and show better CO tolerance than Pt(111). The calculated free energy plots are always downhill for ORR catalyzed by BeN2 in both acid and alkaline environments, and by MgN2 in alkaline environments. The detailed reaction mechanism analyses show that high-efficient four-electron pathway is the optimal pathway for ORR catalyzed by BeN2 in acid environments. Surprisingly, there is a low overpotential of 0.45 eV for ORR catalyzed by BeN2 in the acid solution and no overpotential in the alkaline solution. Our studies found for the first time that 2D h-BeN2 shows huge potential as a non-precious metal ORR catalyst in acid and alkaline environments.

15.
J Med Chem ; 62(24): 10927-10954, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31419130

RESUMO

As a receptor tyrosine kinase of insulin receptor (IR) subfamily, anaplastic lymphoma kinase (ALK) has been validated to play important roles in various cancers, especially anaplastic large cell lymphoma (ALCL), nonsmall cell lung cancer (NSCLC), and neuroblastomas. Currently, five small-molecule inhibitors of ALK, including Crizotinib, Ceritinib, Alectinib, Brigatinib, and Lorlatinib, have been approved by the U.S. Food and Drug Administration (FDA) against ALK-positive NSCLCs. Novel type-I1/2 and type-II ALK inhibitors with improved kinase selectivity and enhanced capability to combat drug resistance have also been reported. Moreover, the "proteolysis targeting chimera" (PROTAC) technique has been successfully applied in developing ALK degraders, which opened a new avenue for targeted ALK therapies. This review provides an overview of the physiological and biological functions of ALK, the discovery and development of drugs targeting ALK by focusing on their chemotypes, activity, selectivity, and resistance as well as potential therapeutic strategies to overcome drug resistance.

16.
Nanoscale ; 11(23): 11351-11359, 2019 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-31166347

RESUMO

To improve the catalytic activity of copper nanoparticles (Cu NPs) in the electro-chemical catalysis of the CO2 reduction reactions (CO2RRs), the formation and use of core/shell nanoparticles (CSNPs) with Cu as the shell composite may be an effective way. Using Cu79 NP as the representative, we performed computational screening and confirmed four Mx@Cu79-x CSNPs that can stably exist. Then, the catalytic performance of the screened CSNPs was tested through first-principles calculations. The free energy profiles indicate that Fe19@Cu60 is more desirable for CO2RR catalysis due to its high selectivity for CO rather than HCOOH at a low potential. Moreover, when it electro-catalyzes CO2 into CH4, the Fe19@Cu60 CSNP exhibits much lower limiting potential (-0.58 V) compared with pure Cu79 NP (-0.86 V) or the Cu (211) surface (-0.70 V). Taking the cost into consideration, the Fe19@Cu60 CSNP is highly recommended as a promising electro-catalyst for CO2RRs. In addition, when CO is taken as the initial reactant to be reduced, all the screened CSNPs exhibit lower limiting potentials than Cu79 NP. From the view of material design, the significant weakening of CO binding originating from the change in the d-band center could be the reason why the formation of a core/shell structure will enhance the catalytic performance of Cu NPs in CO reduction.

17.
Nat Commun ; 10(1): 2149, 2019 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-31089139

RESUMO

Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. Here, we report one single atom W6+ doped Ni(OH)2 nanosheet sample (w-Ni(OH)2) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm2. Moreover, at high current density of 80 mA/cm2, the overpotential value is 267 mV. The corresponding Tafel slope is measured to be 33 mV/dec. The d0 W6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH- groups being adsorbed on the exposed W sites of the Ni(OH)2 nanosheet. Density functional theory (DFT) calculations confirm that the O radical and O-O coupling are both generated at the same site of W6+. This work demonstrates that W6+ doping can promote the electrocatalytic water oxidation activity of Ni(OH)2 with the highest performance.

18.
J Colloid Interface Sci ; 551: 130-137, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31075627

RESUMO

In this work, we reported a comprehensive first-principles study on the hydrogen evolution reaction (HER) catalytic activity of Cu based core-shell nanoparticles (CSNPs). Cu55 nanoparticle (NP) and Mx@Cu55-x CSNPs (x = 1, 13) with Fe, Ru, and Os as core components were constructed and their structural parameters, stability, and electronic properties were calculated. We found that there exist competing effects during the binding of H atom on the NP surface. The competing effects between the decreasing of negative charge on surface Cu atoms and the surface expansion resulted from the change of core port size and atoms affect hydrogen adsorption oppositely. Among these CSNPs, Os13@Cu42 exhibited the best HER catalytic performance with moderate adsorption for H atoms (Eads = -0.20 eV), low Gibbs free energies of hydrogen adsorption (ΔGH = 0.03 eV) and acceptable reaction barrier for H2 generation (Eb = 0.32 eV), which makes it highly promising as HER electro-catalyst.

19.
Nano Lett ; 19(6): 4151-4157, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31117764

RESUMO

X-type ligands, for example, the pair of oleylamine (OAm) and oleic acid (OA), have been widely used to prepare CsPbX3 nanocrystals (NCs). However, the proton exchange between coordinated OAm and OA may induce the detachment of ligands, resulting in poor performance after cleaning or long-time storage. Herein, density functional theory calculations predict that primary amines (L-type ligands) can stabilize a PbBr x-rich surface and yield a trap-free material with fully delocalized valence band maximum and conduction band minimum states, which can significantly improve the photophysical properties and stability of CsPbBr3 NCs. Along this prediction, a room-temperature reprecipitation method using L-type ligands (OAm, n-octylamine, or undecylamine) as the sole capping ligand has been developed to synthesize high-quality CsPbBr3 NCs with near-unity photoluminescence quantum yield and dramatically improved stability against purification and water treatment. The enhancement can be attributed to the strong binding of unprotonated amines to lead atoms and the effective surface passivation provided by the resulted PbBr x-rich surface, which are highly consistent with the theoretical predictions. This work not only offers an approach to synthesize high-quality perovskite NCs but also provides an in-depth understanding of the surface modification of CsPbX3 NCs for practical applications.

20.
J Phys Chem Lett ; 10(11): 2869-2873, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31088074

RESUMO

Recently, some organic-inorganic hybrid perovskites (OIHPs) have been reported to exhibit strong subgap broadband luminescence. While the origin of such luminescence has been proposed by several groups, a strategy to prepare OIHP with the desired subgap emission properties has remained elusive. Here, we report controlled synthesis of a broadband-emitting single-crystal 2D OIHP with an average quantum yield of >80 %. We demonstrate that the intensity of broadband emission can be tuned by controlling the excess iodine ion concentration during the synthesis in hydroiodic acid. We show that the emitters exhibit characteristics of localized defects such as limited mobility and saturation at high excitation power. Using density functional theory calculations, we show that bond-state iodine interstitials are responsible for the observed long-lived luminescence.

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