Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 78
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nanotechnology ; 2020 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-32150739

RESUMO

Poly 3, 4-ethylenedioxythiophene (PEDOT) and its derivative polymers are attractive for electronic applications because of their high conductivity and circumstance stability. The fabrication of PEDOT devices generally takes a separated strategy for EDOT polymerization and then device fabrication. This makes PEDOT device fabrication complex and un-friendly for integration. For the insolubility of PEDOT in common solution, material modification including vinyl moiety group grafting on the side chain of PEDOT can be used to improve its solubility, but it will markedly reduce the conductivity. Here we report on direct laser writing of pure EDOT monomer into PEDOT with 140 nm feature size. The PEDOT nanowire possesses high conductivity of 1.28×105S/m and can be patterned on solid and flexible substrates with various structures, which paved the way towards organic high conductive device fabrication and integration.

2.
Nanomaterials (Basel) ; 9(11)2019 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-31744070

RESUMO

In this work, TiO2 QDs-modified NiO nanosheets were employed to improve the room temperature NO2 sensing properties of NiO. The gas sensing studies showed that the response of nanocomposites with the optimal ratio to 60 ppm NO2 was nearly 10 times larger than that of bare NiO, exhibiting a potential application in gas sensing. Considering the commonly reported immature mechanism that the effective charge transfer between two phases contributes to an enhanced sensitivity, the QDs sensitization mechanism was further detailed by designing a series of contrast experiments. First, the important role of the QDs size effect was revealed by comparing the little enhanced sensitivity of TiO2 particle-modified NiO with the largely enhanced sensitivity of TiO2 QDs-NiO. Second, and more importantly, direct evidence of the heterointerface charge transfer efficiency was detailed by the extracted interface bond (Ti-O-Ni) using XPS peak fitting. This work can thus provide guidelines to design more QDs-modified nanocomposites with higher sensitivity for practical applications.

3.
Chem Commun (Camb) ; 55(89): 13386-13389, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31633713

RESUMO

The formation path of hollow complex nanocages prepared via Na2WO4·2H2O etching, using Prussian blue as a template, is tracked, which confirms the existence of a central cross structure inside the etching products. A mechanism based on etching along edges is described. The gas sensor designed with an Fe-W hollow complex exhibits excellent performance toward CH3S3CH3.

4.
Appl Opt ; 58(24): 6611-6617, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31503592

RESUMO

An electrically controlled arc-electrode liquid-crystal microlens array (AE-LCMLA), with tuning and swing focus, is proposed, which can be utilized to replace the traditional mechanically controlled microlenses and also cooperate with photosensitive arrays to solve the problems of measuring and further adjusting a strong distortion wavefront. The top patterned electrode of a single LC microlens is composed of three arc-electrodes distributed symmetrically around a central microhole for constructing the key controlling structures of the LC cavity in the AE-LCMLA. All the arc-electrodes are individually controlled, and then the focal spot of each microlens can be moved freely in a three-dimensional fashion including along the optical axial direction and over the focal plane by simply adjusting the driving signal voltage applied over each arc-electrode, independently. The featured performances of the AE-LCMLA in a wavelength range of ∼501-561 nm are the driving signal voltage being relatively low (less than ∼11 Vrms), the focal length tuning range being from ∼2.54 mm to ∼3.50 mm, the maximum focus swing distance being ∼52.92 µm, and the focus swing ratio K being ∼20‰.

5.
Opt Express ; 27(16): 23422-23431, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31510618

RESUMO

A new type of electrically controlled liquid-crystal microlens matrix (EC-LCMM) with a nested electrode array for efficiently tuning and swinging focus, which means that the focus position can be adjusted in three dimensions, is proposed. The EC-LCMM is constructed by a 10 × 10 arrayed annular-sector-shaped aluminum electrode with a central microhole of 140µm diameter and three annular-sectors of 210µm external diameter and the period length of 280µm. To the arrangement of the patterned electrode, both the 10 × 10 LC microlens array based on the annular-sector-shaped aluminum electrode and the 9 × 9 LC microlens array based on an arrayed quasi-quadrilateral-ring-shaped electrode can be obtained. The 9 × 9 LC microlens array is formed by matching adjacent four annular-sector-shaped sub-electrodes in the 10 × 10 LC microlenses. The developed EC-LCMM can be used to electrically tune focus along the optical axis and also swing focus over a focal plane selected. The typical performances include: electrically tunable focusing in a driving voltage range of 3~7Vrms, the focal length in a range of 2~0.6mm, and the maximum focus swing distance being 16µm. For effectively describing the focus swing efficiency, the parameters of SF and SA are defined, which are the ratios between the focus swinging distance and the current focal length along the optical axis, and between the focus swinging extent and the external diameter of a single annular-sector-shaped aluminum electrode, respectively. The SF and SA of the EC-LCMM are ~16‰ and ~7.6%, respectively. It can be expected that the complex wavefront can be more efficiently measured and adjusted according to the EC-LCMM-based Shack-Hartmann wavefront measuring and adjusting architecture.

6.
Chem Commun (Camb) ; 55(74): 11045-11048, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31453574

RESUMO

Ag NPs are encapsulated into ZIF-71 via a deposition-reduction method. The resulting products are tested as adjustable molecular sieves for hydrogen and acetone. The gas sensing performances show that the response to acetone is reduced and that to hydrogen increased, demonstrating an engineered selectivity. A novel design of molecular sieving MOF materials for gas separation in gas-sensing selectivity is thus provided.

7.
ACS Appl Mater Interfaces ; 11(22): 20535-20544, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31081609

RESUMO

For the stretchable electrode, strong interface adhesion is the primary guarantee for long service life, and the maximization of the tensile limit with remarkable electrical stability can expand the scope of its use. Here, a cost-effective strategy is proposed to fabricate a high-adhesion stretchable electrode. By modifying dopamine and functionalized silane on a polydimethylsiloxane (PDMS) substrate in sequence before the electroless deposition process, super-high adhesion up to 3.1 MPa is achieved between the PDMS substrate and silver layer, and the electrode exhibits extraordinary conductivity of 4.0 × 107 S/m. This process is also suitable for other common flexible substrates and metals. Moreover, inspired by the micro-/nanostructure on the surface of lotus leaf, a biomimetic elastomeric micropore film with a uniformly distributed micropore is fabricated by the one-step soft lithography replication process. The electrode exhibits a large tensile limit exceeding 70% uniaxial tensile and superior electrical stability from 6.3 to 11.5 Ω under 20% uniaxial tensile for more than 10 000 cycles. This study seeks a promising method to manufacture stretchable electrodes with high adhesion, large tensile limit, and excellent electrical stability, showing great potential to detect various biological signals including joint movement, surface electromyography, and so forth.

8.
Small ; 15(10): e1804559, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30714294

RESUMO

Flexible pressure sensors as electronic skins have attracted wide attention to their potential applications for healthcare and intelligent robotics. However, the tradeoff between their sensitivity and pressure range restricts their practical applications in various healthcare fields. Herein, a cost-effective flexible pressure sensor with an ultrahigh sensitivity over an ultrawide pressure-range is developed by combining a sandpaper-molded multilevel microstructured polydimethylsiloxane and a reduced oxide graphene film. The unique multilevel microstructure via a two-step sandpaper-molding method leads to an ultrahigh sensitivity (2.5-1051 kPa-1 ) and can detect subtle and large pressure over an ultrawide range (0.01-400 kPa), which covers the overall pressure regime in daily life. Sharp increases in the contact area and additional contact sites caused by the multilevel microstructures jointly contribute to such unprecedented performance, which is confirmed by in situ observation of the gap variations and the contact states of the sensor under different pressures. Examples of the flexible pressure sensors are shown in potential applications involving the detection of various human physiological signals, such as breathing rate, vocal-cord vibration, heart rate, wrist pulse, and foot plantar pressure. Another object manipulation application is also demonstrated, where the material shows its great potential as electronic skin intelligent robotics and prosthetic limbs.

9.
Micromachines (Basel) ; 10(2)2019 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-30791375

RESUMO

A new dual-mode liquid-crystal (LC) micro-device constructed by incorporating a Fabry⁻Perot (FP) cavity and an arrayed LC micro-lens for performing simultaneous electrically adjusted filtering and zooming in infrared wavelength range is presented in this paper. The main micro-structure is a micro-cavity consisting of two parallel zinc selenide (ZnSe) substrates that are pre-coated with ~20-nm aluminum (Al) layers which served as their high-reflection films and electrodes. In particular, the top electrode of the device is patterned by 44 × 38 circular micro-holes of 120 µm diameter, which also means a 44 × 38 micro-lens array. The micro-cavity with a typical depth of ~12 µm is fully filled by LC materials. The experimental results show that the spectral component with needed frequency or wavelength can be selected effectively from incident micro-beams, and both the transmission spectrum and the point spread function can be adjusted simultaneously by simply varying the root-mean-square value of the signal voltage applied, so as to demonstrate a closely correlated feature of filtering and zooming. In addition, the maximum transmittance is already up to ~20% according the peak-to-valley value of the spectral transmittance curves, which exhibits nearly twice the increment compared with that of the ordinary LC-FP filtering without micro-lenses.

10.
Langmuir ; 35(9): 3248-3255, 2019 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-30759983

RESUMO

The detection of trace amount of volatile organic compounds (VOCs) has been covered by tons of researches, which are dedicated to improve the detection limit and insensitivity to humidity. In this work, we have synthesized ZnO@ZIF-71 nanorod arrays (NRAs) equipped with the adsorption effect at metal site that promoted the detection limit of ethanol and acetone, to which also have great selectivity. The gas sensor not only exhibits shorter response/recovery time (53/55% for ethanol, 48/31% for acetone), but also excellent insensitivity to humidity and improved detection limit (10× improved at 21 ppb for ethanol, 4× at 3 ppb for acetone) at low working temperature (150 °C). By the analysis of in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and calculation of density functional theory (DFT), the mechanism of enhanced gas sensing performance from ZnO@ZIF-71 NRAs is proved. It shows ethanol and acetone gas molecules can be adsorbed at the metal sites of ZIF-71. This work provides a new idea to improve the detection limit and humidity-insensitivity of gas sensor toward specific gas molecules.

11.
Opt Lett ; 43(22): 5551-5554, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30439893

RESUMO

In this Letter, all-optical generation of magnetization with arbitrary three-dimensional (3D) orientations is numerically demonstrated through the inverse Faraday effect (IFE) by using a reversing calculation method. The IFE-induced magnetization with an expected 3D orientation is initially conceived by coherently configuring two orthogonally arranged electric dipoles with a phase difference of π/2 in the focal region of a to-be-determined incident light field. Based on the dipole antenna theory, this required incident light field can be deduced analytically according to the orientations of the electric dipoles. By utilizing this field as illumination and reversing the field propagation, magnetization with the expected orientation can be obtained in the focal region through the IFE. Moreover, this method showcases a high magnetization orientation purity (greater than 93%) within the focal volume defined by the full width at half maximum when the numerical aperture of the focal lens is 0.95. This result demonstrates extended flexibility of magnetization manipulations in an all-optical fashion and possesses great potential in spintronics and all-optical magnetic recording.

12.
ACS Sens ; 3(12): 2629-2636, 2018 12 28.
Artigo em Inglês | MEDLINE | ID: mdl-30456951

RESUMO

Black and blue phosphorus (both allotropes of elementary phosphorus) have recently been widely explored as an active material for electronic devices, and their potential in gas sensing applications has been demonstrated. On the other hand, amorphous red phosphorus (a-RP), a much cheaper and readily available phosphorus allotrope, has seldom been investigated as an electronic material, and its gas sensing properties have never been studied. In this work we have investigated these properties of a-RP by combining experimental characterizations with theoretical calculations. We found that a-RP exhibited an amphoteric character for detecting both commonly regarded reducing and oxidizing gas molecules, featuring a negative correlation between the electrical resistance of a-RP and the gas concentration. Interestingly, the a-RP based sensors appear to be particularly suitable for room-temperature NO2 detection, exhibiting excellent sensitivity and selectivity, as well as fast temporal response and recovery. A unique sensing feature of a-RP toward NO2 was identified, which is associated with the expansion of P-P bonds upon NO2 chemisorption. Based on density functional theory calculations we proposed a physiochemical model to elaborate the synergistic effects of the P-P bond expansion and Langmuir isotherm adsorption on the electronic properties and gas sensing processes of a-RP.


Assuntos
Dióxido de Nitrogênio/análise , Fósforo/química , Semicondutores , Adsorção , Teoria da Densidade Funcional , Técnicas Eletroquímicas/métodos , Gases/análise , Gases/química , Modelos Químicos , Dióxido de Nitrogênio/química , Oxirredução , Temperatura Ambiente
13.
Langmuir ; 34(48): 14577-14585, 2018 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-30423250

RESUMO

In this work, we report a metal-organic framework (MOF)-assisted strategy to synthesize necklace-like TiO2/Co3O4 nanofibers with highly ordered heterostructures via a facile approach including electrospinning and subsequent calcination. Polycrystalline TiO2 nanofibers and Co3O4 nanocages are consummately interconnected to form a highly ordered heterogeneous nanostructure, which can be of benefit for precisely accommodating the interface resistance of the p-n heterojunctions and the future realization of improved material performance. The ethanol-gas-sensing investigation showed that TiO2/Co3O4 nanofiber sensors exhibited a strong ethanol response ( Rair/ Rgas -1 = 16.7 @ 150 ppm) and a low operating temperature of 150 °C. The sensing enhancement mechanism of the TiO2/Co3O4 nanofibers is related to the formation of heterojunctions at interfaces and the high catalytic activity of MOF-derived Co3O4. Furthermore, this versatile method is a promising approach to constructing ordered heterostructures and extending the MOF-based heterogeneous materials toward wide applications.

14.
Opt Express ; 26(4): 4035-4049, 2018 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-29475259

RESUMO

Light-field imaging is a crucial and straightforward way of measuring and analyzing surrounding light worlds. In this paper, a dual-polarized light-field imaging micro-system based on a twisted nematic liquid-crystal microlens array (TN-LCMLA) for direct three-dimensional (3D) observation is fabricated and demonstrated. The prototyped camera has been constructed by integrating a TN-LCMLA with a common CMOS sensor array. By switching the working state of the TN-LCMLA, two orthogonally polarized light-field images can be remapped through the functioned imaging sensors. The imaging micro-system in conjunction with the electric-optical microstructure can be used to perform polarization and light-field imaging, simultaneously. Compared with conventional plenoptic cameras using liquid-crystal microlens array, the polarization-independent light-field images with a high image quality can be obtained in the arbitrary polarization state selected. We experimentally demonstrate characters including a relatively wide operation range in the manipulation of incident beams and the multiple imaging modes, such as conventional two-dimensional imaging, light-field imaging, and polarization imaging. Considering the obvious features of the TN-LCMLA, such as very low power consumption, providing multiple imaging modes mentioned, simple and low-cost manufacturing, the imaging micro-system integrated with this kind of liquid-crystal microstructure driven electrically presents the potential capability of directly observing a 3D object in typical scattering media.

15.
Sci Rep ; 8(1): 207, 2018 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-29317686

RESUMO

The effect of microstructure on the impact toughness and the temper embrittlement of a SA508Gr.4N steel was investigated. Martensitic and bainitic structures formed in this material were examined via scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and Auger electron spectroscopy (AES) analysis. The martensitic structure had a positive effect on both the strength and toughness. Compared with the bainitic structure, this structure consisted of smaller blocks and more high-angle grain boundaries (HAGBs). Changes in the ultimate tensile strength and toughness of the martensitic structure were attributed to an increase in the crack propagation path. This increase resulted from an increased number of HAGBs and refinement of the sub-structure (block). The AES results revealed that sulfur segregation is higher in the martensitic structure than in the bainitic structure. Therefore, the martensitic structure is more susceptible to temper embrittlement than the bainitic structure.

16.
Rev Sci Instrum ; 88(3): 033111, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28372436

RESUMO

A liquid crystal microlens array (LCMLA) with an arrayed microhole pattern electrode based on nematic liquid crystal materials using a fabrication method including traditional UV-photolithography and wet etching is presented. Its focusing performance is measured under different voltage signals applied between the electrodes of the LCMLA. The experimental outcome shows that the focal length of the LCMLA can be tuned easily by only changing the root mean square value of the voltage signal applied. The developed LCMLA is further integrated with a main lens and an imaging sensor to construct a LCMLA-based focused plenoptic camera (LCFPC) prototype. The focused range of the LCFPC can be shifted electrically along the optical axis of the imaging system. The principles and methods for acquiring several key parameters such as three dimensional (3D) depth, positioning, and motion expression are given. The depth resolution is discussed in detail. Experiments are carried out to obtain the static and dynamic 3D information of objects chosen.

17.
Appl Opt ; 56(7): 1925-1929, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28248390

RESUMO

An electrically tunable infrared (IR) filter based on a key cascaded liquid-crystal Fabry-Perot (C-LC-FP) working in the wavelength range of 3-5 µm is presented. The C-LC-FP is constructed by closely stacking two FP microcavities with different depths of 12 and 15 µm and fully filled by nematic LC materials. Through continuous wavelength selection of both microcavities, radiation with a high transmittance and narrow bandwidth can pass through the filter. According to the electrically controlled birefringence characteristics of nematic LC molecules, the transmission spectrum can be shifted through applying a dual voltage signal over the C-LC-FP. Compared with common LC-FPs with a single microcavity, the C-LC-FP demonstrates better transmittance peak morphology and spectral selection performance. To be more specific, the number and the shifted scope of the IR transmission peak can be decreased and widened, respectively.

18.
Appl Opt ; 56(6): 1788-1794, 2017 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-28234391

RESUMO

Based on our fundamental work on liquid-crystal microlens arrays (LCMAs) driven and adjusted electrically, a new kind of arrayed optical switch (AOS) constructed by a key LCMA with a special dual-mode function of converging and diverging incident beams according to electrical signals applied over the LCMA is proposed. The LCMA leading to the AOS is constructed by a microcavity with a couple of paralleled electrodes. The top electrodes of the LCMA are fabricated by depositing a layer of indium-tin-oxide (ITO) film and a layer of aluminum film, respectively. The aluminum film is continuously patterned into a circular microhole array, and the ITO film only acts as a planar conductor. Both functioning films are effectively separated by the SiO2 wafer. Another SiO2 wafer is also coated by an ITO film as a planar conductor. The measurements show that the developed AOS can effectively switch on or off beams propagating in arrayed fibers by applying proper voltage signals to them. Compared with other conventional AOSs, the developed AOS demonstrates several merits, including greater integration level, lower cost, and suitability to high-power propagating beams.

19.
Phys Chem Chem Phys ; 19(9): 6313-6329, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28198897

RESUMO

Metal-oxide-semiconductor (MOS) based gas sensors have been considered a promising candidate for gas detection over the past few years. However, the sensing properties of MOS-based gas sensors also need to be further enhanced to satisfy the higher requirements for specific applications, such as medical diagnosis based on human breath, gas detection in harsh environments, etc. In these fields, excellent selectivity, low power consumption, a fast response/recovery rate, low humidity dependence and a low limit of detection concentration should be fulfilled simultaneously, which pose great challenges to the MOS-based gas sensors. Recently, in order to improve the sensing performances of MOS-based gas sensors, more and more researchers have carried out extensive research from theory to practice. For a similar purpose, on the basis of the whole fabrication process of gas sensors, this review gives a presentation of the important role of screening and the recent developments in high throughput screening. Subsequently, together with the sensing mechanism, the factors influencing the sensing properties of MOSs involved in material preparation processes were also discussed in detail. It was concluded that the sensing properties of MOSs not only depend on the morphological structure (particle size, morphology, pore size, etc.), but also rely on the defect structure and heterointerface structure (grain boundaries, heterointerfaces, defect concentrations, etc.). Therefore, the material-sensor integration was also introduced to maintain the structural stability in the sensor fabrication process, ensuring the sensing stability of MOS-based gas sensors. Finally, the perspectives of the MOS-based gas sensors in the aspects of fundamental research and the improvements in the sensing properties are pointed out.

20.
Phys Chem Chem Phys ; 19(16): 10695-10697, 2017 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-27352959

RESUMO

Correction for 'Enhanced room temperature NO2 response of NiO-SnO2 nanocomposites induced by interface bonds at the p-n heterojunction' by Jian Zhang et al., Phys. Chem. Chem. Phys., 2016, 18, 5386-5396.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA