Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 29
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Chem Inf Model ; 60(1): 47-55, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31825611

RESUMO

Synthesis planning is the process of recursively decomposing target molecules into available precursors. Computer-aided retrosynthesis can potentially assist chemists in designing synthetic routes; however, at present, it is cumbersome and cannot provide satisfactory results. In this study, we have developed a template-free self-corrected retrosynthesis predictor (SCROP) to predict retrosynthesis using transformer neural networks. In the method, the retrosynthesis planning was converted to a machine translation problem from the products to molecular linear notations of the reactants. By coupling with a neural network-based syntax corrector, our method achieved an accuracy of 59.0% on a standard benchmark data set, which outperformed other deep learning methods by >21% and template-based methods by >6%. More importantly, our method was 1.7 times more accurate than other state-of-the-art methods for compounds not appearing in the training set.

2.
Appl Opt ; 58(22): 5936-5941, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31503909

RESUMO

Circular dichroism (CD) of metasurfaces has been used in biological monitoring, analytical chemistry, and perfect polarization converters. In this work, a metasurface consisting of nanoholes and tilted nanorods is proposed to achieve the CD effect. Numerical calculations show that electrical current forms between the film and the tilted nanorods under circularly polarized light illumination, and CD effects originate from the coupling between the current oscillations at the film and those on the tilted nanorods. This electrical oscillation mode provides unique coupling mechanisms for the CD effect. In addition, CD is strongly dependent on the structural parameters, and the resonant modes can be tuned by modulating the currents on the film. These results are helpful for designing novel chiral optical structures and provide unique methods for circular polarizers.

3.
Molecules ; 24(13)2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31269689

RESUMO

Lithium-collaborating organic batteries (Li-[28]hexs) were investigated with [28]hexaphyrin(1.1.1.1.1.1) as an active electrode material. Each hexaphyrin of [28]Hex cathode ideally involved four electrons per unit cycle and performed a typical charge/discharge processes of Li-organic battery. Li-[28]Hex batteries set with fast charging rates showed reasonably stable charge and discharge performances over 200 cycles even though it caused incomplete (2~3 electrons) charge/discharge cycles due to failing the complete charging process. UV absorption changes of [28]hexaphyrin in CH2Cl2 were supplementary for the electrochemical oxidation, which performed a conversion from [28]hexaphyrin to [26]hexaphyrin.


Assuntos
Fontes de Energia Elétrica , Lítio/química , Porfirinas/química , Cor , Eletroquímica , Eletrodos , Conformação Molecular , Oxirredução
4.
ACS Appl Mater Interfaces ; 11(8): 7661-7665, 2019 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-30702269

RESUMO

To enhance the electron transfer within the covalent organic frameworks (COFs), we obtained a nanocomposite of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) and redox-active AQ-COF by performing a facile in situ solid-state polymerization inside the nanochannels of COFs. The PEDOT chains functioned like electron highways within the nanochannels, resulting in a PEDOT@AQ-COF nanocomposite with an excellent electrical conductivity of 1.1 S cm-1 and a remarkably improved performance in faradaic energy storage. The all-organic PEDOT@AQ-COF electrode showed specific capacitance as high as 1663 F g-1 (at 1 A g-1), ultrafast charge/discharge rate performance (998 F g-1 at 500 A g-1), and excellent stability for 10 000 cycles. This research demonstrates a promising strategy for increasing the conductivity of COF-based materials and broadening their applications.

5.
Appl Opt ; 58(1): 177-181, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30645527

RESUMO

Circular dichroism (CD) of nanostructures is in great demand for applications in biological molecules, photocurrent devices, and photocatalysis. Planar nanostructures can be prepared in a concise manner, and their CD effects have gained much research interest. In this study, tilted zigzag-shaped nanohole (TZSN) arrays are proposed, and the CD effect is studied by the finite element method. A strong resonance occurs in the gap by tuning the charge distributions between adjacent nanoholes. Meanwhile, the CD effect of TZSN arrays is strongly dependent on the structural parameters of TZSN. Results provide a novel method for tuning the CD effects of nanohole arrays on a film.

6.
Macromol Rapid Commun ; 40(6): e1800708, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30468541

RESUMO

Transparent coatings with antireflection, antifogging, antifrosting, antifouling, and moisture self-cleaning properties can dramatically improve the efficiency and convenience of optical elements and thus are highly desirable for practical applications. Here, it is demonstrated that a bionic nanocone surface (BNS) fabricated by a facile, low-cost process consisting of template-assisted prepolymer curing followed by surface modification can possess the multiple functions listed above. The polymer coating firmly adheres to a glass substrate due to bonding agents. After SiO2 nanoparticle deposition and low-surface-energy fluorosilane modification, the coating shows low microdroplet adhesion. As a result, the as-prepared BNS exhibits a high transmittance when exposed to fog and good clarity even when the temperature decreases to -20 °C in a humid environment. Dipping the BNS into exemplified graphite powder has almost no influence on the transparency, and the BNS can realize self-cleaning of moisture when the surface is covered with a thick layer of man-made contaminants.


Assuntos
Nanopartículas/química , Polímeros/química , Dióxido de Silício/química , Umidade , Tamanho da Partícula , Propriedades de Superfície
7.
Appl Opt ; 57(23): 6721-6724, 2018 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-30129627

RESUMO

Circular dichroism (CD) is a signal that characterizes the optical properties of chiral structures. Structures with intense CD signals have valuable applications in molecular chemistry, pharmaceuticals, and biosensing. This work proposes the use of a nanowire to increase the CD signal of crossed nanorods. The separation of resonant wavelengths of transmission under left-handed and right-handed circular polarization incidence (LCP and RCP) increases because the electric interaction between the upper nanorod and nanowire under LCP incidence is different from that under RCP incidence. The increased separation of resonant wavelengths, in turn, enhances the CD signals. In addition, two new CD modes appear, and these modes can be tuned by changing the structural parameters of the proposed structure. The present results will guide the design of plasmonic chiral nanostructures for enhancing the CD signal.

8.
J Phys Condens Matter ; 30(11): 114001, 2018 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-29400659

RESUMO

Asymmetric transmission (AT) is widely used in polarization transformers and polarization-controlled devices. In this paper, a planar metamaterial nanostructure with connected gammadion-shaped nanostructure (CGN) is proposed to achieve AT effect for forward and backward propagations of circular polarized light. The CGN arrays can produce magnetic moment oscillation that is normal to the metamaterial plane, which is weakly coupled to free space and generates transmission valleys. The introduction of symmetry breaking exerts a strong influence on the AT effects, and these effects can be tuned by the structural parameters. Our planar metamaterials may have potential for application in the future design of polarization-controlling devices.

9.
Opt Express ; 26(2): 1199-1205, 2018 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-29401996

RESUMO

Asymmetric transmission (AT) holds significant applications in controlling polarization and propagation directions of electromagnetic waves. In this paper, tilted rectangular nanohole (TRNH) arrays in a square lattice are proposed to realize an AT effect. Numerical results show two AT modes in the transmission spectrum, and they are ascribed to the localized surface plasmon resonances around the two ends of TRNH and surface plasmon polaritons on the golden film. AT properties of the TRNH strongly depend on structural parameters, such as width, length, thickness, and tilted angle of TRNH. Results provide a novel mechanism for generating AT effect and offer potential plasmonic device applications, such as asymmetric wave splitters and optical isolators.

10.
Opt Express ; 25(24): 29659-29666, 2017 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-29221003

RESUMO

Plasmonic bending beams, which preserve their spatial shapes while propagating along curved trajectories in metal-dielectric interface, offer important applications in the fields of fiber sensor, optical trapping, and micro-nano manipulation. In this work, circular hole array, as a local point-like sources of surface plasmon polaritons, is designed on the metal film to generate multiple plasmonic bending beams. The electric field intensity of multiple plasmonic bending beams is controlled by polarization angle of input light. In addition, the electric filed intensity of multiple plasmonic bending beams relies on circle hole radius. These findings provide guidance in the design and optimization of plasmonic bending beam generators.

11.
Adv Mater ; 29(46)2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29058350

RESUMO

Chemical vapor deposition growth of 1T' ReS2x Se2(1-x) alloy monolayers is reported for the first time. The composition and the corresponding bandgap of the alloy can be continuously tuned from ReSe2 (1.32 eV) to ReS2 (1.62 eV) by precisely controlling the growth conditions. Atomic-resolution scanning transmission electron microscopy reveals an interesting local atomic distribution in ReS2x Se2(1-x) alloy, where S and Se atoms are selectively occupied at different X sites in each Re-X6 octahedral unit cell with perfect matching between their atomic radius and space size of each X site. This structure is much attractive as it can induce the generation of highly desired localized electronic states in the 2D surface. The carrier type, threshold voltage, and carrier mobility of the alloy-based field effect transistors can be systematically modulated by tuning the alloy composition. Especially, for the first time the fully tunable conductivity of ReS2x Se2(1-x) alloys from n-type to bipolar and p-type is realized. Owing to the 1T' structure of ReS2x Se2(1-x) alloys, they exhibit strong anisotropic optical, electrical, and photoelectric properties. The controllable growth of monolayer ReS2x Se2(1-x) alloy with tunable bandgaps and electrical properties as well as superior anisotropic feature provides the feasibility for designing multifunctional 2D optoelectronic devices.

12.
Opt Express ; 25(20): 24623-24629, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-29041407

RESUMO

A strong chiral near-field is crucial for the detection of chiral molecules. Active tuning of the chiral near-field can shorten the detection process. In this study, a graphene-based achiral nanoring (GAN) that can actively control chiral near-fields is presented. The GAN is composed of three identical graphene pieces. The handedness and strength of the chiral near-fields can be actively controlled by adjusting the Fermi levels of these three graphene pieces. The optical chirality of the GAN near-field is 500 times that of circularly polarized light. In addition, the GAN enhances the chiral response of the chiral material by a factor of 250. This work provides opportunities for the ultrasensitive detection and location of molecules through the active control of chiral near-fields.

13.
Appl Opt ; 56(20): 5781-5785, 2017 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-29047724

RESUMO

Asymmetric transmission (AT) has significant applications in optical polarization control. In this paper, we propose a kind of periodic nanoslit rather than the protruding planar structures, such as G-shaped structure and coupled split-ring resonators, to realize the AT effect. The planar periodic obliquely intersecting nanoslits (OINs) in the gold film, composed of gratings with an infinite length and tilted nanoslits with a finite length, are proposed to realize the AT effect by performing the finite element method. Obvious dips in the AT spectra result from the circular localized surface plasmon resonance around the two terminals of the tilted nanoslits and from the surface plasmon polariton resonances on the film and in the gratings or tilted nanoslits. In addition, the AT effect strongly depends on the geometric parameters of the OINs. The film can be straightly powered on as an in-plane electrical conductor, which broadens its applications in optoelectronic devices. Overall, these results are beneficial in designing devices to achieve AT for polarization transformation.

14.
Opt Lett ; 42(14): 2842-2845, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28708183

RESUMO

The circular dichroism (CD) effect plays an important role in biological detection, analytical chemistry, and plasmonic sensing. Tilted 3D structures can generate CD signals under normal illumination. However, fabricating tilted 3D structures is complex and expensive. In this study, we fabricate a tilted U-shaped nanostructure (TUSN) on a polystyrene (PS) nanosphere through the glancing angle deposition method. One branch of the U-shaped nanostructure is tilted by raising a sheet of SiO2 on the PS nanosphere. And the CD signal of the TUSN is enhanced because the phase difference increases with increasing thickness of the SiO2 sheet. This work proposes a method for fabricating tilted nanostructures and elucidates the mechanism of the CD effect for future research.

15.
Opt Express ; 25(5): 5480-5487, 2017 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-28380808

RESUMO

Circular dichroism (CD) is useful in molecular chemistry, pharmaceuticals, and bio-sensing. In this paper, twisted Z-shaped nanostructure (TZN) is proposed to achieve giant CD. The TZN is composed of three vertical and twisted nanorods. Given that the resonance of vertical nanorod is only observable for left circularly polarized light excitation but is subdued for right circularly polarized light excitation, which leads to the giant CD effect approaching 88%. The subdued resonance of vertical nanorod can be excited by rotating the bottom nanorod. The CD properties can be tuned by the length of nanorods and the gap between them. These results would guide the design of plasmonic chiral nanostructures for achieving giant CD effect.

16.
J Nanosci Nanotechnol ; 17(1): 377-81, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-29620838

RESUMO

Gold bilayered slit arrays with rectangular holes embedded into the metal surface are designed to enhance the circular dichroism (CD) effect of gold bilayered slit arrays. The rectangular holes in these arrays block electric currents and generate localized surface plasmons around these holes, thereby strengthening the CD effect. The CD enhancement factor depends strongly on the rotational angle and the structural parameters of the rectangular holes; this factor can be enhanced further by drilling two additional rectangular holes into the metal surfaces of the arrays. These results help facilitate the design of chiral structures to produce a strong CD effect and large electric fields.

17.
Nanoscale ; 8(45): 18956-18962, 2016 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-27805226

RESUMO

As an anisotropic 2D layered material, rhenium disulfide (ReS2) has attracted much attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, the low lattice symmetry and interlayer decoupling of ReS2 make asymmetric growth and out-of-plane growth occur quite easily; therefore, thick flake, dendritic and flower-like structures of ReS2 have mostly been obtained previously. Here, we report on an approach based on space-confined epitaxial growth for the controlled synthesis of ReS2 films. Using this approach, large-area and high-quality ReS2 films with uniform monolayer thickness can grow on a mica substrate. Furthermore, the weak van der Waals interaction between the surface of mica and ReS2 clusters, which favors surface-confined growth while avoiding out-of-plane growth, is critical for growing ReS2 with uniform monolayer thickness. The morphological evolution of ReS2 with the growth temperature reveals that asymmetric growth can be suppressed at relatively low temperatures. A ReS2 field-effect transistor displayed a current on/off ratio of 106 and an electron mobility of up to 40 cm2 V-1 s-1, with outstanding photoresponsivity of 12 A W-1. This work not only promotes the large-scale employment of ReS2 in high-performance optoelectronic devices, but also provides a means of controlling the unusual growth behavior of low-lattice-symmetry 2D layered materials.

18.
Adv Mater ; 28(25): 5018, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27372721

RESUMO

H. Xu, J. Zhang, and co-workers synthesize anisotropic 2D-layered rhenium disulfide with high crystal quality and uniform monolayer thickness. As described on page 5019, tellurium-assisted epitaxial growth on a mica substrate is chosen to generate such structures.

19.
Opt Express ; 24(15): 16425-33, 2016 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-27464094

RESUMO

Circular dichroism (CD) and asymmetric transmission (AT) are important in the field of negative refractive index media and perfect polarization converters. A large difference between T++ and T-- in the transmission matrix T leads to a large CD effect, whereas a large difference between T-+ and T+- leads to a large AT effect. To achieve large CD and AT effects simultaneously, we theoretically analyzed the transmission matrix T and proposed the chiral plasmonic nanostructure of twist nanoslit-nanorod arrays (TNNAs) in this study. Results calculated by the finite element method show that, at around resonant wavelengths, the spectra of T++ and T-- correspondingly present peaks and valleys leading to a large CD effect. Meanwhile one of the spectra for T-+ and T+- presents valleys and another presents peaks leading to a large AT effect. More importantly, the magnitude of CD is equivalent to that of AT. In addition, the CD and AT effects strongly depend on the geometric parameters of TNNAs. Overall, these results are useful for designing chiral plasmonic nanostructures with large CD and AT effects.

20.
Adv Mater ; 28(25): 5019-24, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27121002

RESUMO

Anisotropic 2D layered material rhenium disulfide (ReS2 ) with high crystal quality and uniform monolayer thickness is synthesized by using tellurium-assisted epitaxial growth on mica substrate. Benefit from the lower eutectic temperature of rhenium-tellurium binary eutectic, ReS2 can grow from rhenium (melting point at 3180 °C) and sulfur precursors in the temperature range of 460-900 °C with high efficiency.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA