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1.
ACS Nano ; 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31934744

RESUMO

Nacre, an organic-inorganic composite biomaterial that forms an ordered multilayer microstructure after years of slow biomineralization, is known as the strongest and toughest material within the mollusc family. Its unique structure provides inspiration for robust artificial engineering materials. Lignocellulose is ultralightweight, abundant, and possesses a high mechanical performance, is used for ages as a significant renewable raw material in wooden engineering composites. However, the inherent lack of mechanical properties of current wooden composites associated with the fragile microstructure has limited their applications in advanced engineering materials. Here, we develop a large-size ultralightweight artificial "wood nacre" with an ordered layer structure through a fast and scalable "mechanical/chemical mineralization and assembly" approach. The millimeter-thick artificial wooden nacre mimics the stratified construction of natural nacre, resulting in a bulk hybrid material that can achieve the almost same strength as natural nacre while consisting of only 1/6 of the total inorganic content of natural nacre. The specific strength and toughness of the artificial wooden nacre is even superior to engineering alloy materials (such as Cu and Fe). This approach represents an efficient strategy for the mass production of lightweight sustainable structural materials with high strength and toughness.

2.
Chem Commun (Camb) ; 55(98): 14761-14764, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31754679

RESUMO

We develop a pre-sodiation method by simply immersing the electrode in a liquid sodium source to reduce irreversible capacity loss for titanium-based materials. This liquid is more safe in operation and penetrates through the electrode more homogeneously than sodium metal. This method is easily extended to other titanium-based materials, and provides a possibility for large industrial applications.

3.
Nat Commun ; 10(1): 4728, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31624241

RESUMO

Two-dimensional molecular crystals, consisting of zero-dimensional molecules, are very appealing due to their novel physical properties. However, they are mostly limited to organic molecules. The synthesis of inorganic version of two-dimensional molecular crystals is still a challenge due to the difficulties in controlling the crystal phase and growth plane. Here, we design a passivator-assisted vapor deposition method for the growth of two-dimensional Sb2O3 inorganic molecular crystals as thin as monolayer. The passivator can prevent the heterophase nucleation and suppress the growth of low-energy planes, and enable the molecule-by-molecule lateral growth along high-energy planes. Using Raman spectroscopy and in situ transmission electron microscopy, we show that the insulating α-phase of Sb2O3 flakes can be transformed into semiconducting ß-phase under heat and electron-beam irradiation. Our findings can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.

4.
ACS Appl Mater Interfaces ; 11(44): 41374-41382, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31613087

RESUMO

Many research efforts for advanced Li-ion batteries have been made to design new material with large capacity and long cycle life, but little attention has been paid to regulate the voltage platform until now. Although quite attractive for the binary Ge-based chalcogenides, challenge is that a large potential gap as well as incongruous reaction kinetics is typically found between their conversion step (>1.6 V) and alloying region (<0.4 V). Herein, we propose an endogenetic structural design by grafting Sb2Te3 building block into layered GeTe to establish a ternary Ge2Sb2Te5 compound, which can effectively level such a big potential gap. Turning from semiconductive GeTe into metallic conductive Ge2Sb2Te5, the reaction kinetics can be enhanced. The LixTe formation step in Ge2Sb2Te5 is found declined to 1.30 V, and the enlistment of Sb (∼0.78 V) bridges the conversion and alloying plateau; thus, the incongruous reaction kinetics and large potential gap between the conversion-alloying step can be alleviated. Furthermore, there is a spatially confined and synergistic effect among Te, Sb, and Ge components, conducting the LixTe and LixGe processes in a more harmonious and gentle way. Therefore, Ge2Sb2Te5 exhibites much enhanced cyclability and rate performance, with 546 mAh/g remained at 2000 mA/g. This unique design strategy can be leveraged to manipulate the voltage profile of other compounds.

5.
Small ; 15(44): e1903496, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31489786

RESUMO

Recently, Bi-doped Cs2 Ag0.6 Na0.4 InCl6 lead-free double perovskites demonstrating efficient warm-white emission have been reported. To enable the solution processing and enrich the application fields of this promising material, here a colloidal synthesis of Cs2 Ag1- x Nax In1- y Biy Cl6 nanocrystals is further developed. Different from its bulk states, the emission color temperatures of the nanocrystal can be tuned from 9759.7 to 4429.2 K by Na+ and Bi3+ incorporation. Furthermore, the newly developed nanocrystals can break the wavefunction symmetry of the self-trapped excitons by partial replacement of Ag+ ions with Na+ ions and consequently allow radiative recombination. Assisted with Bi3+ ions doping and ligand passivation, the photoluminescence quantum yield of the Cs2 Ag0.17 Na0.83 In0.88 Bi0.12 Cl6 nanocrystals is further promoted to 64%, which is the highest value for lead-free perovskite nanocrystals at present. The new colloidal nanocrystals with tunable color temperature and efficient photoluminescence are expected to greatly advance the research progress of lead-free perovskites in single-emitter-based white emitting materials and devices.

6.
Small ; 15(44): e1903159, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31483559

RESUMO

Semimetal 1T' MoTe2 crystals have attracted tremendous attention owing to their anisotropic optical properties, Weyl semimetal, phase transition, and so on. However, the complex refractive indices (n-ik) of the anisotropic semimetal 1T' MoTe2 still are not revealed yet, which is important to applications such as polarized wide spectrum detectors, polarized surface plasmonics, and nonlinear optics. Here, the linear dichroism of as-grown trilayer 1T' MoTe2 single crystals is investigated. Trilayer 1T' MoTe2 shows obvious anisotropic optical absorption due to the intraband transition of dz 2 orbits for Mo atoms and px orbits for Te atoms. The anisotropic complex refractive indices of few-layer 1T' MoTe2 are experimentally obtained for the first time by using the Pinier equation analysis. Based on the linear dichroism of 1T' MoTe2 , angle-resolved polarized optical microscopy is developed to visualize the grain boundary and identify the crystal orientation of 1T' MoTe2 crystals, which is also an excellent tool toward the investigation of the optical absorption properties in the visible range for anisotropic 2D transition metal chalcogenides. This work provides a universal and nondestructive method to identify the crystal orientation of anisotropic 2D materials, which opens up an opportunity to investigate the optical application of anisotropic semimetal 2D materials.

7.
ACS Nano ; 13(8): 9028-9037, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31408313

RESUMO

As an emerging two-dimensional semiconductor, Bi2O2Se has recently attracted broad interests in optoelectronic devices for its superior mobility and ambient stability, whereas the diminished photoresponse near its inherent indirect bandgap (0.8 eV or λ = 1550 nm) severely restricted its application in the broad infrared spectra. Here, we report the Bi2O2Se nanosheets based hybrid photodetector for short wavelength infrared detection up to 2 µm via PbSe colloidal quantum dots (CQDs) sensitization. The type II interfacial band offset between PbSe and Bi2O2Se not only enhanced the device responsivity compared to bare Bi2O2Se but also sped up the response time to ∼4 ms, which was ∼300 times faster than PbSe CQDs. It was further demonstrated that the photocurrent in such a zero-dimensional-two-dimensional hybrid photodetector could be efficiently tailored from a photoconductive to photogate dominated response under external field effects, thereby rendering a sensitive infrared response >103 A/W at 2 µm. The excellent performance up to 2 µm highlights the potential of field-effect modulated Bi2O2Se-based hybrid photodetectors in pursuing highly sensitive and broadband photodetection.

8.
Chem Soc Rev ; 48(17): 4639-4654, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31410435

RESUMO

Research on 2D materials has recently become one of the hottest topics that has attracted broad interdisciplinary attention. 2D materials offer fascinating platforms for fundamental science and technological explorations at the nanometer scale and molecular level, and exhibit diverse potential applications for future advanced nano-photonics and electronics. The chemical vapor deposition (CVD) technique has shown great promise for producing high-quality 2D materials with superior electro-optical performance. However, it is difficult to synthesize continuous single-crystal 2D materials with large domain sizes and good uniformity due to the low vapor pressure of their precursors. It has been observed that the addition of selected synergistic additives to the CVD process under mild conditions can result in uniformly large-area and highly crystalline monolayer 2D materials with exceptional optical/electrical properties. Moreover, the 2D material-based devices chemically modified by synergistic additives can achieve superior performances compared to those previously reported. In this review, we compare several typical synergistic additive-mediated CVD growth processes of 2D materials, as well as their superior properties, and provide some perspectives and challenges for the future of this emerging research field.

9.
Nat Commun ; 10(1): 3331, 2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31350401

RESUMO

Ferroelectric engineered pn doping in two-dimensional (2D) semiconductors hold essential promise in realizing customized functional devices in a reconfigurable manner. Here, we report the successful pn doping in molybdenum disulfide (MoS2) optoelectronic device by local patterned ferroelectric polarization, and its configuration into lateral diode and npn bipolar phototransistors for photodetection from such a versatile playground. The lateral pn diode formed in this way manifests efficient self-powered detection by separating ~12% photo-generated electrons and holes. When polarized as bipolar phototransistor, the device is customized with a gain ~1000 by its transistor action, reaching the responsivity ~12 A W-1 and detectivity over 1013 Jones while keeping a fast response speed within 20 µs. A promising pathway toward high performance optoelectronics is thus opened up based on local ferroelectric polarization coupled 2D semiconductors.

10.
Nano Lett ; 19(8): 5410-5416, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31343178

RESUMO

Piezoelectric two-dimensional (2D) van der Waals (vdWs) materials are highly desirable for applications in miniaturized and flexible/wearable devices. However, the reverse-polarization between adjacent layers in current 2D layered materials results in decreasing their in-plane piezoelectric coefficients with layer number, which limits their practical applications. Here, we report a class of 2D layered materials with an identical orientation of in-plane polarization. Their piezoelectric coefficients (e22) increase with layer number, thereby allowing for the fabrication of flexible piezotronic devices with large piezoelectric responsivity and excellent mechanical durability. The piezoelectric outputs can reach up to 0.363 V for a 7-layer α-In2Se3 device, with a current responsivity of 598.1 pA for 1% strain, which is 1 order of magnitude higher than the values of the reported 2D piezoelectrics. The self-powered piezoelectric sensors made of these newly developed 2D layered materials have been successfully used for real-time health monitoring, proving their suitability for the fabrication of flexible piezotronic devices due to their large piezoelectric responses and excellent mechanical durability.

11.
Small ; 15(35): e1901364, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31282127

RESUMO

Low threshold micro/nanolasers have attracted extensive attention for wide applications in high-density storage and optical communication. However, constrained by quantum efficiency and crystalline quality, conventional semiconductor small-sized lasers are still subjected to a high lasing threshold. In this work, a low-threshold planar laser based on high-quality single-crystalline hexagonal CdS nanoplatelets (NPLs) using a self-limited epitaxial growth method is demonstrated. The as-grown CdS NPLs show multiple whispering-gallery-mode lasing at room temperature with a threshold of ≈0.6 µJ cm-2 , which is the lowest value among reported CdS-based lasers. Through power-dependent lasing studies at 77 K, the lasing action is demonstrated to originate from a exciton-exciton scattering process. Furthermore, the edge length- and thickness-dependent lasing threshold studies reveal that the threshold is inversely proportional to the second power of lateral edge length while partially affected by vertical thickness, and the lasing modes can be sustained in NPLs as thin as 60 nm. The lowest threshold emerges with the thickness of ≈110 nm due to stronger energy confinement in the vertical Fabry-Pérot cavity. The results not only open up a new avenue to fabricate nonlayered material-based coherent light sources, but also advocate the promise of nonlayered semiconductor materials for the development of novel optoelectronic devices.

12.
Adv Mater ; 31(36): e1903580, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31339207

RESUMO

2D planar structures of nonlayered wide-bandgap semiconductors enable distinguished electronic properties, desirable short wavelength emission, and facile construction of 2D heterojunction without lattice match. However, the growth of ultrathin 2D nonlayered materials is limited by their strong covalent bonded nature. Herein, the synthesis of ultrathin 2D nonlayered CuBr nanosheets with a thickness of about 0.91 nm and an edge size of 45 µm via a controllable self-confined chemical vapor deposition method is described. The enhanced spin-triplet exciton (Zf , 2.98 eV) luminescence and polarization-enhanced second-harmonic generation based on the 2D CuBr flakes demonstrate the potential of short-wavelength luminescent applications. Solar-blind and self-driven ultraviolet (UV) photodetectors based on the as-synthesized 2D CuBr flakes exhibit a high photoresponsivity of 3.17 A W-1 , an external quantum efficiency of 1126%, and a detectivity (D*) of 1.4 × 1011 Jones, accompanied by a fast rise time of 32 ms and a decay time of 48 ms. The unique nonlayered structure and novel optical properties of the 2D CuBr flakes, together with their controllable growth, make them a highly promising candidate for future applications in short-wavelength light-emitting devices, nonlinear optical devices, and UV photodetectors.

13.
ACS Appl Mater Interfaces ; 11(26): 23353-23360, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31187617

RESUMO

Two-dimensional (2D) GeSe is an important IVA-VIA semiconductor for future applications in electronics and optoelectronics because of its high absorption coefficient, mobility, and photoresponsivity. However, the controllable synthesis of 2D GeSe flakes is still a huge problem. Here, high-quality single-crystalline ultrathin 2D GeSe flakes are synthesized by a salt-assisted chemical vapor deposition method. The flakes tend to grow along the [010] crystal orientation presenting a rectangular shape with a thickness down to 5 nm. Then, the electrical and optoelectronic properties have been systematically investigated. A thickness-dependent Schottky barrier is shown in GeSe field-effect transistors. The p-type conductivity of GeSe is mainly caused by the Ge deficiency, which is proven by a variable-temperature experiment and theoretical calculations. In addition, the phototransistors based on as-grown GeSe flakes present an ultrahigh responsivity of 1.8 × 104 A/W and an excellent external quantum efficiency of 4.2 × 106%.

14.
ACS Nano ; 13(6): 7291-7299, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31188571

RESUMO

The piezo-phototronic effect has been promising as an effective means to improve the performance of two-dimensional (2D) semiconductor based optoelectronic devices. However, the current reported monolayer 2D semiconductors are not regarded as suitable for actual flexible piezotronic photodetectors due to their insufficient optical absorption and mechanical durability, although they possess strong piezoelectricity. In this work, we demonstrate that, unlike 2H-phase transition-metal dichalcogenides, γ-phase InSe with a hexagonal unit cell possesses broken inversion symmetry in all the layer numbers and has a strong second-harmonic generation effect. Moreover, driven by the piezo-phototronic effect, a flexible self-powered photodetector based on multilayer γ-InSe, which can work without any energy supply, is proposed. The device exhibited ultrahigh photon responsivity of 824 mA/W under light illuminations of 400 nm (0.368 mW/cm2). Moreover, the responsivity and response speed of this photodetector were enhanced further by as much as 696% and 1010%, respectively, when a 0.62% uniaxial tensile strain was applied. Our devices exhibit high reliability and stability during a 6 month test time. These significant findings offer a promising pathway to construct high-performance flexible piezo-phototronic photodetectors based on multilayer 2D semiconductors.

15.
Adv Mater ; 31(28): e1900528, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31116896

RESUMO

Integrating thermodynamically favorable ethanol reforming reactions with hybrid water electrolysis will allow room-temperature production of high-value organic products and decoupled hydrogen evolution. However, electrochemical reforming of ethanol has not received adequate attention due to its low catalytic efficiency and poor selectivity, which are caused by the multiple groups and chemical bonds of ethanol. In addition to the thermodynamic properties affected by the electronic structure of the catalyst, the dynamics of molecule/ion dynamics in electrolytes also play a significant role in the efficiency of a catalyst. The relatively large size and viscosity of the ethanol molecule necessitates large channels for molecule/ion transport through catalysts. Perforated CoNi hydroxide nanosheets are proposed as a model catalyst to synergistically regulate the dynamics of molecules and electronic structures. Molecular dynamics simulations directly reveal that these nanosheets can act as a "dam" to enrich ethanol molecules and facilitate permeation through the nanopores. Additionally, the charge transfer behavior of heteroatoms modifies the local charge density to promote molecular chemisorption. As expected, the perforated nanosheets exhibit a small potential (1.39 V) and high Faradaic efficiency for the conversion of ethanol into acetic acid. Moreover, the concept in this work provides new perspectives for exploring other molecular catalysts.

16.
Adv Mater ; 31(27): e1900342, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31095799

RESUMO

Commercial deployment of lithium anodes has been severely impeded by the poor battery safety, unsatisfying cycling lifespan, and efficiency. Recently, building artificial interfacial layers over a lithium anode was regarded as an effective strategy to stabilize the electrode. However, the fabrications reported so far have mostly been conducted directly upon lithium foil, often requiring stringent reaction conditions with indispensable inert environment protection and highly specialized reagents due to the high reactivity of metallic lithium. Besides, the uneven lithium-ion flux across the lithium surface should be more powerfully tailored via mighty interfacial layer materials. Herein, g-C3 N4 is employed as a Li+ -modulating material and a brand-new autotransferable strategy to fabricate this interfacial layer for Li anodes without any inert atmosphere protection and limitation of chemical regents is developed. The g-C3 N4 film is filtrated on the separator in air using a common alcohol solution and then perfectly autotransferred to the lithium surface by electrolyte wetting during normal cell assembly. The abundant nitrogen species within g-C3 N4 nanosheets can form transient LiN bonds to powerfully stabilize the lithium-ion flux and thus enable a CE over 99% for 900 cycles and smooth deposition at high current densities and capacities, surpassing most previous works.

17.
ACS Nano ; 13(6): 6297-6307, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31082203

RESUMO

Two-dimensional (2D) materials exhibit high sensitivity to structural defects due to the nature of interface-type materials, and the corresponding structural defects can effectively modulate their inherent properties in turn, giving them a wide application range in high-performance and functional devices. 2D γ-Ga2S3 is a defective semiconductor with outstanding optoelectronic properties. However, its controllable preparation has not been implemented yet, which hinders exploring its potential applications. In this work, we introduce nonlayered γ-Ga2S3 into the 2D materials family, which was successfully synthesized via the space-confined chemical vapor deposition method. Its intriguing defective structure are revealed by high-resolution transmission electron microscopy and temperature-dependent cathodoluminescence spectra, which endow the γ-Ga2S3-based device with a broad photoresponse from the ultraviolet to near-infrared region and excellent photoelectric conversion capability. Simultaneously, the device also exhibits excellent ultraviolet detection ability ( Rλ = 61.3 A W-1, Ion /Ioff = 851, EQE = 2.17× 104 %, D* = 1.52× 1010 Jones @350 nm), and relatively fast response (15 ms). This work provides a feasible way to fabricate ultrathin nonlayered materials and explore the potential applications of a 2D defective semiconductor in high-performance broadband photodetection, which also suggests a promising future of defect creation in optimizing photoelectric properties.

18.
Small ; 15(30): e1901347, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31111680

RESUMO

Infrared (IR) photodetectors are finding diverse applications in imaging, information communication, military, etc. 2D metal chalcogenides (2DMCs) have attracted increasing interest in view of their unique structures and extraordinary physical properties. They have demonstrated outstanding IR detection performance including high responsivity and detectivity, high on/off ratio, fast response rate, stable room temperature operability, and good mechanical flexibility, which has opened up a new prospect in next-generation IR photodetectors. This Review presents a comprehensive summary of recent progress in advanced IR photodetectors based on 2DMCs. The rationale of the photodetectors containing photocurrent generation mechanisms and performance parameters are briefly introduced. The device performances of 2DMCs-based IR photodetectors are also systematically summarized, and some representative achievements are highlighted as well. Finally, conclusions and outlooks are delivered as a guideline for this thriving field.

19.
ACS Appl Mater Interfaces ; 11(21): 19623-19630, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31056914

RESUMO

Enhancing the light extraction efficiency is a prevalent but vital challenge for most solid-state lighting technologies, especially for deep ultraviolet light-emitting diodes (DUV-LEDs). In this paper, inspired by the microstructure of the butterfly's eye, we propose and fabricate a flexible fluoropolymer film (FFP film) to tackle this issue for all-mode, full-wavelength light extraction enhancement for most solid-state lighting technologies compatibly. The experimental results demonstrate that compared with one mounted with a smooth FFP film, the light output power of DUV-LED is enhanced up to 26.7% by mounting the FFP film with 325 nm radius nanocones at a driving current of 200 mA. Importantly, thanks to the super-flexible feature of the FFP film, it can both cover the top surface and sidewalls of the DUV-LED chip, leading to the improvement of transverse electric and transverse magnetic mode light extraction by 20.5 and 21.8%, respectively. Finite element analysis (FEA) simulations of the electric field distribution of DUV-LEDs with the FFP film reveal the underlying physics. The present strategy is proposed from the view of the packaging level, which is cost-effective, able to be manufactured at a large scale, and compatible with the solid-state lighting technologies.

20.
ACS Appl Mater Interfaces ; 11(17): 15905-15912, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30964268

RESUMO

Compared with their 3D counterparts, layered 2D Ruddlesden-Popper perovskites (2D RPPs) with the formula of (A')2A n-1Pb nX3 n+1 exhibit improved photo and moisture stability. To develop flexible single-crystalline electronics and wearable devices, cost-effective growth of large-area single crystals of 2D RPPs with large lateral size, ultrathin thickness, parallel orientation, and well-defined and controlled n values are highly desirable, but it remains still a challenge. Here, we modified the space-confined aqueous solution growth method to fabricate single-crystalline films of (BA)2(MA) n-1Pb nX3 n+1 and n = 1, 2, 3, respectively, with the lateral size reaching millimeter and thickness about 400-1000 nm. Moreover, the quantum well layers are found to be parallel to the substrate, well suitable for lateral transport requirement. We successfully integrated ultrathin single crystals of (BA)2(MA) n-1Pb nX3 n+1 ( n = 1-3) into a metal-semiconductor-metal two-terminal photodetector. The photoresponsive wavelength range was extended from 525 nm for n = 1 and 590 nm for n = 2 to 630 nm for n = 3 as a result of the reduced exciton band gap. The device of n = 2 single crystals shows the highest responsivity of 2.96 A/W and a detectivity of 1013 jones, while the device of n = 3 shows the lowest dark current 10-14 A, and therefore, its on/off ratio reaches 2862 at the bias voltage of 1 V.

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