Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nat Commun ; 11(1): 541, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992713

RESUMO

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.

2.
Adv Mater ; 31(39): e1901964, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31389096

RESUMO

Atomically thin oxychalcogenides have been attracting intensive attention for their fascinating fundamental properties and application prospects. Bi2 O2 Se, a representative of layered oxychalcogenides, has emerged as an air-stable high-mobility 2D semiconductor that holds great promise for next-generation electronics. The preparation and device fabrication of high-quality Bi2 O2 Se crystals down to a few atomic layers remains a great challenge at present. Here, molecular beam epitaxy (MBE) of atomically thin Bi2 O2 Se films down to monolayer on SrTiO3 (001) substrate is achieved by co-evaporating Bi and Se precursors in oxygen atmosphere. The interfacial atomic arrangements of MBE-grown Bi2 O2 Se/SrTiO3 are unambiguously revealed, showing an atomically sharp interface and atom-to-atom alignment. Importantly, the electronic band structures of one-unit-cell (1-UC) thick Bi2 O2 Se films are observed by angle-resolved photoemission spectroscopy (ARPES), showing low effective mass of ≈0.15 m0 and bandgap of ≈0.8 eV. These results may be constructive to the synthesis of other 2D oxychalcogenides and investigation of novel physical properties.

3.
ACS Appl Mater Interfaces ; 10(34): 29092-29099, 2018 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-30074380

RESUMO

It is a widely used strategy to enhance gas sensor sensitivity by improving its surface area, but this process, including bonding the sensing block into a device substrate, needs complex manipulations. This work shows a concept of creating adsorption active sites, in which an SnO2 layer (6.85 nm thin) is directly coated on a triangle array substrate to be of an ensemble of triangular convex adsorption active sites (TCAASs). The resultant SnO2 gas sensors, with TCAAS periods ranging from 289 to 1154 nm, exhibit an adsorption-active-site-dependent sensitivity and present a low detection limit of around 6 ppm ethanol gas at room temperature. By characterizations of Kelvin force microscopy, a large surface potential variation exists on these adsorption active sites after introducing ethanol gas, distinctly showing a local adsorption enhancement. These results confirm that the creation of adsorption active sites can efficiently increase surface adsorption of a sensor to realize its sensitive gas-sensing.

4.
ACS Appl Mater Interfaces ; 10(16): 13895-13902, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29595250

RESUMO

Adsorption-induced change of carrier density is presently dominating inorganic semiconductor gas sensing, which is usually operated at a high temperature. Besides carrier density, other carrier characteristics might also play a critical role in gas sensing. Here, we show that carrier mobility can be an efficient parameter to dominate gas sensing, by which room-temperature gas sensing of inorganic semiconductors is realized via a carrier mobility-dominated gas-sensing (CMDGS) mode. To demonstrate CMDGS, we design and prepare a gas sensor based on a regular array of SnO2 nanorods on a bottom film. It is found that the key for determining the gas-sensing mode is adjusting the length of the arrayed nanorods. With the change in the nanorod length from 340 to 40 nm, the gas-sensing behavior changes from the conventional carrier-density mode to a complete carrier-mobility mode. Moreover, compared to the carrier density-dominating gas sensing, the proposed CMDGS mode enhances the sensor sensitivity. CMDGS proves to be an emerging gas-sensing mode for designing inorganic semiconductor gas sensors with high performances at room temperature.

5.
Chempluschem ; 83(8): 741-755, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31950669

RESUMO

High sensitivity imposes strict requirements on a sensing platform, for which nanostructured arrays are promising candidates. The template-assisted method is an effective strategy to prepare various nanostructured arrays, which are widely developed for different sensing applications. Herein, nanostructured array based sensing platforms prepared from four widely used templates, a colloidal monolayer, anodic aluminum oxide, block copolymer, and a nanoimprint mold, are reviewed. In a series of sensing applications (e.g., biosensing and gas sensing), the resulting nanostructure-array-based platforms are high sensitive owing to their advanced morphology features: 1) high-density alignment of arrayed nanostructures, 2) high surface-to-volume ratio, and 3) convex-rich morphology. In surface-enhanced Raman spectroscopy (SERS) applications, noble-metal particle arrays with high-density alignment produce an enhanced SERS signal owing to a strong concentration of plasmonic resonance on the substrate. To sense biomolecules in solution and gaseous molecules, arrays with a high surface-to-volume ratio or convex-rich morphology can sensitively respond to changes in the environment. Moreover, the nanostructure-array-based sensing platforms are divided into three types (0D, 1D, and 3D nanostructured arrays) to demonstrate the morphological origin of the sensing performances.

6.
ACS Nano ; 11(7): 7382-7389, 2017 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-28671810

RESUMO

Plasmonic nanostructures have been widely incorporated into different semiconductor materials to improve solar energy conversion. An important point is how to manipulate the incident light so that more light can be efficiently scattered and absorbed within the semiconductors. Here, by using a tunable three-dimensional Au pillar/truncated-pyramid (PTP) array as a plasmonic coupler, a superior optical absorption of about 95% within a wide wavelength range is demonstrated from an assembled CdS/Au PTP photoanode. Based on incident photon to current efficiency measurements and the corresponding finite difference time domain simulations, it is concluded that the enhancement is mainly attributed to an appropriate spectral complementation between surface plasmon resonance modes and photonic modes in the Au PTP structure over the operational spectrum. Because both of them are wavelength-dependent, the Au PTP profile and CdS thickness are further adjusted to take full advantage of the complementary effect, and subsequently, an angle-independent photocurrent with an enhancement of about 400% was obtained. The designed plasmonic PTP nanostructure of Au is highly robust, and it could be easily extended to other plasmonic metals equipped with semiconductor thin films for photovoltaic and photoelectrochemical cells.

7.
ACS Appl Mater Interfaces ; 8(5): 3428-37, 2016 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-26829014

RESUMO

A new general method for the fabrication of a reduced graphene oxide (rGO)-based ordered monolayer macroporous film composed of a layer of closely arranged pores is introduced. Assisted by the polystyrene microsphere monolayer colloid crystal by a simple solution-heated method, pure rGO, rGO-SnO2, rGO-Fe2O3, and rGO-NiO composite monolayer ordered porous films were examplarily constructed on the curved surface of a ceramic tube widely used in gas sensors. The rGO-oxide composite porous films could exhibit much better sensing performances than those of the corresponding pure oxide films and the composite films without the ordered porous structures in detecting ethanol gas. The enhancement mechanisms induced by distinctive rGO-oxide heterojunctions and porous structures as well as the effects of the rGO content and the pore-size on the sensitivity of the composite films were systematically analyzed and discussed. This study opens up a kind of construction method for an rGO-based composite film gas sensor with uniform surface structures and high performance.

8.
Sci Rep ; 5: 8939, 2015 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-25758292

RESUMO

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties.

9.
ACS Appl Mater Interfaces ; 6(2): 1251-7, 2014 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-24410862

RESUMO

A new photochemistry-based method was introduced for fabricating SnO2 monolayer ordered porous films with size-tunable surface pores on ceramic tubes used for gas sensors. The growth of the spherical pore walls was controlled by two times irradiation of the ultraviolet light using polystyrene microsphere two-dimensional colloidal crystal as a template. The surface pore size of the final obtained porous films was well tuned by changing the second irradiation time rather than replacing the template microspheres. The monolayer ordered porous films on the tubes were directly used, for the first time, as gas sensors. The sensitivity of the sensor depended on the surface pore size and was carefully analyzed by ethanol gas detection. The sensor also exhibited short response-recovery time and long-term stability at lower than 300 °C in practical applications. Therefore, this study opens up a kind of construction method for gas sensors, provides a new strategy for controlling the surface pore size of the monolayer ordered porous film, and introduces a new type of sensitivity-controllable gas sensor.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA