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1.
Nanoscale Res Lett ; 14(1): 371, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31820137

RESUMO

The near-infrared (NIR) photoelectric properties of multilayer Bi2O2Se nanofilms were systematically studied in this paper. Multilayer Bi2O2Se nanofilms demonstrate a sensitive photo response to NIR, including a high photoresponsivity (~ 101 A/W), a quick response time (~ 30 ms), a high external quantum efficiency (~ 20,300%), and a high detection rate (1.9 × 1010 Jones). These results show that the device based on multilayer Bi2O2Se nanofilms might have great potentials for future applications in ultrafast, highly sensitive NIR optoelectronic devices.

2.
Small ; 15(43): e1904482, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31512402

RESUMO

Bi2 O2 Se is emerging as a photosensitive functional material for optoelectronics, and its photodetection mechanism is mostly considered to be a photoconductive regime in previous reports. Here, the bolometric effect is discovered in Bi2 O2 Se photodetectors. The coexistence of photoconductive effect and bolometric effect is generally observed in multiwavelength photoresponse measurements and then confirmed with microscale local heating experiments. The unique photoresponse of Bi2 O2 Se photodetectors may arise from a change of hot electrons during temperature rises instead of photoexcited holes and electrons. Direct proof of the bolometric effect is achieved by real-time temperature tracking of Bi2 O2 Se photodetectors under time evolution after light excitation. Moreover, the Bi2 O2 Se bolometer shows a high temperature coefficient of resistance (-1.6% K-1 ), high bolometric coefficient (-31 nA K-1 ), and high bolometric responsivity (>320 A W-1 ). These findings offer a new approach to develop bolometric photodetectors based on Bi2 O2 Se layered materials.

3.
Nanomaterials (Basel) ; 9(8)2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31370164

RESUMO

Controllably tuned infrared emissivity has attracted great interest for potential application in adaptive thermal camouflage. In this work, we report a flexible multilayer graphene based infrared device on a porous polyethylene membrane, where the infrared emissivity could be tuned by ionic liquid intercalation. The Fermi level of surface multilayer graphene shifts to a high energy level through ionic liquid intercalation, which blocks electronic transition below the Fermi level. Thus, the optical absorptivity/emissivity of graphene could be controlled by intercalation. Experimentally, the infrared emissivity of surface graphene was found to be tuned from 0.57 to 0.41 after ionic liquid intercalation. Meanwhile, the relative reflectivity Rv/R0 of surface graphene increased from 1.0 to 1.15. The strong fluorescence background of Raman spectra, the upshift of the G peak (~23 cm-1), and the decrease of sheet resistance confirmed the successful intercalation of ionic liquid into the graphene layers. This intercalation control of the infrared emissivity of graphene in this work displays a new way of building an effective thermal camouflage system.

4.
Nanotechnology ; 30(43): 435702, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31323650

RESUMO

Monolayer graphene has high symmetrical crystal structure and exhibits in-plane isotropic physical properties. However, twisted bilayer graphene (tBLG) is expected to differ physically, due to the broken symmetry introduced by the interlayer coupling between adjacent graphene layers. This symmetry breaking is usually accompanied by in-plane anisotropy in their electrical, optical and thermal properties. However, the existence of in-plane anisotropy in tBLG has remained evasive until now. Here, an unambiguous identification of the in-plane anisotropy in tBLG is established by angle-resolved polarized Raman spectroscopy. It was found that the double-resonant two-dimensional band is anisotropic. The degree of in-plane anisotropy is found to be dependent on the misorientation angles, which is two- and four-fold for tBLG with misorientation angles of 15° and 20°, respectively. This finding adds a new dimension to the properties of graphene, which opens a possibility to the development of graphene-based angle-resolved photonics and electronics.

5.
Medicine (Baltimore) ; 98(28): e16443, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31305472

RESUMO

BACKGROUND: Upper respiratory tract infections (URTIs) is a common disease in children, which is also known as the common cold. Pediatric Tuina is a common treatment that Traditional Chinese Medicine (TCM) doctors commonly use for URTIs. However, there has no relevant systematic review studied on its effects and safety been reported. We plan to perform a systematically reviewing of all the clinical evidence on the effectiveness and safety of Tuina for URTIs in children. METHODS: We will conduct the literature searching in the following electronic databases: Pubmed, Embase, Cochrane Library, Web of science, Chinese National Knowledge Infrastructure (CNKI), VIP, Wanfang, China Biomedical Literature Database (CBM), Chinese Clinical Trial Registry System. The time limit for retrieving studies is from establishment to July 2019 for each database. All published randomized controlled trials (RTCs) related to this review will be included. Review Manager (V.5.3.5) will be implemented for the assessment of bias risk and data analyses. Subgroup analysis and sensitivity analysis will be performed based on the conditions of included data. RESULTS: A high-quality synthesis of current evidence of Tuina for children with URTIs will be provided in this study. CONCLUSION: This systematic review will provide evidence of whether Tuina is an effective intervention for children with URTIs. PROSPERO REGISTRATION NUMBER: CRD42019126963.


Assuntos
Medicina Tradicional Chinesa , Metanálise como Assunto , Modalidades de Fisioterapia , Infecções Respiratórias/terapia , Revisão Sistemática como Assunto , Criança , Pré-Escolar , Humanos , Lactente , Recém-Nascido , Ensaios Clínicos Controlados Aleatórios como Assunto , Projetos de Pesquisa
6.
Nanomaterials (Basel) ; 9(5)2019 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-31137613

RESUMO

This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer of BSS demonstrates PL redshift, Raman E 2 g 1 mode redshift, and lower PL intensity. Spatial inhomogeneity of PL and Raman are also observed in the BSS. Based on theoretical analysis, these exotic effects can be attributed to substrate-coupling-induced strain and doping. Our findings provide pertinent insight into film-substrate interaction, and are of great significance to researches on bilayer-stacked structures including twisted bilayer structure, Van der Waals hetero- and homo-structure.

7.
Opt Express ; 26(16): 20174-20182, 2018 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-30119331

RESUMO

In general, there is a fundamental trade-off between the operational bandwidth and the attainable absorption. So, obtaining broadband wave absorption of a low reference standard such as 90% is not very difficult. However, when trying to obtain higher absorption such as 99%, the bandwidth will drop dramatically. Here, we demonstrate that broadband near-perfect absorption of over 99% absorption with a 60% relative bandwidth can be obtained utilizing single-layered and nonstructured graphene loaded with periodical dielectric wires. The absorption mechanism originates from the coupling of Mie resonances in dielectric wires excited by the incident wave to the graphene plasmon resonances, which introduces two absorption contributions: direct near-field absorption in the graphene and radiative emission into the graphene.

8.
ACS Appl Mater Interfaces ; 10(36): 30045-30050, 2018 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-30146869

RESUMO

Growing uniform oxides with various thickness on TMDs is one of the biggest challenges to integrate TMDs into complementary metal oxide semiconductor (CMOS) logic circuits. Here, we report a layer-by-layer oxidation of atomically thin MoTe2 flakes via ozone (O3) exposure. The thickness of MoO x oxide film could be tuning with atomic-level accuracy simply by varying O3 exposure time. Additionally, MoO x-covered MoTe2 shows a hole-dominated transport behavior. Our findings point to a simple and effective strategy for growing homogeneous surface oxide film on MoTe2, which is promising for several purposes in metal-oxide-semiconductor transistor, ranging from surface passivation to dielectric layers.

9.
Nano Lett ; 16(1): 629-36, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26612060

RESUMO

Superconducting layered transition metal dichalcogenides (TMDs) stand out among other superconductors due to the tunable nature of the superconducting transition, coexistence with other collective electronic excitations (charge density waves), and strong intrinsic spin-orbit coupling. Molybdenum disulfide (MoS2) is the most studied representative of this family of materials, especially since the recent demonstration of the possibility to tune its critical temperature, Tc, by electric-field doping. However, just one of its polymorphs, band-insulator 2H-MoS2, has so far been explored for its potential to host superconductivity. We have investigated the possibility to induce superconductivity in metallic polytypes, 1T- and 1T'-MoS2, by potassium (K) intercalation. We demonstrate that at doping levels significantly higher than that required to induce superconductivity in 2H-MoS2, both 1T and 1T' phases become superconducting with Tc = 2.8 and 4.6 K, respectively. Unusually, K intercalation in this case is responsible both for the structural and superconducting phase transitions. By adding new members to the family of superconducting TMDs, our findings open the way to further manipulate and enhance the electronic properties of these technologically important materials.


Assuntos
Dissulfetos/química , Molibdênio/química , Nanoestruturas/química , Potássio/química , Catálise , Calcogênios/química , Condutividade Elétrica , Temperatura Ambiente
10.
Appl Opt ; 52(21): 5230-4, 2013 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-23872771

RESUMO

We investigate the lateral variations of photocurrent on CdS/Al interfaces, with a combination of a semiconductor characterization system and scanning near-field optical microscopy, in which the near-field probe is used to locally induce photocurrent on the CdS/Al interfaces with high spatial resolution. By analyzing the spatially resolved photoresponse, we find that the resolution is worsened in the photocurrent images by the lateral diffusion of the photoexcited electrons and that the photoelectric properties of the CdS/Al interfaces are strongly affected by the bias voltage. Furthermore, in a complementary experiment, we also demonstrate that the photocurrent measurements can reveal structures that are not present in the case of shear-force data. The analysis demonstrates the band structure and microscopic mechanism of CdS/Al heterostructures, which provide an effective approach for developing CdS-based photoelectronic devices.

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