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1.
Nanomaterials (Basel) ; 11(9)2021 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-34578760

RESUMO

We studied the variation in electrical conductivity of exfoliated RuO2 nanosheets and the modulation in the contact resistance of individual nanosheet devices using charge transfer doping effects based on surface metal nanoparticle decorations. The electrical conductivity in the monolayer and bilayer RuO2 nanosheets gradually increased due to the surface decoration of Cu, and subsequently Ag, nanoparticles. We obtained contact resistances between the nanosheet and electrodes using the four-point and two-point probe techniques. Moreover, the contact resistances decreased during the surface decoration processes. We established that the surface decoration of metal nanoparticles is a suitable method for external contact engineering and the modulation of the internal properties of nanomaterials.

2.
Adv Mater ; 33(47): e2005929, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33978972

RESUMO

With the recent reillumination of the hydrogen economy around the world, the demand for H2 sensors is expected to increase rapidly. Due to safety issues caused by the highly flammable and explosive character of hydrogen gas (H2 ), it is imperative to develop the sensors that can quickly and sensitively detect H2 leaks. For the development of H2 sensors, Pd-based materials have been extensively used due to the high affinity of Pd metal for H2 . Among Pd-based H2 sensors, Pd nanogap-based sensors have been extensively investigated because these sensors can operate in an on-off manner, which enables them to have improved sensing capabilities, including high sensitivity, rapid response, short recovery time, and good reliability. Importantly, significant advances in H2 -sensing performance have been achieved by simply using an elastomeric substrate to form Pd nanogaps. Herein, the progress and advanced approaches achieved over the last decade for Pd nanogap-based H2 sensors supported on elastomeric substrates are reviewed, with a focus on strategies to reduce detection limits and increase reliability, sensitivity, and stability.

3.
Sensors (Basel) ; 20(23)2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-33271990

RESUMO

The purpose of our study was to validate a newly developed breath acetone (BrAce) analyzer, and to explore if BrAce could predict aerobic exercise-related substrate use. Six healthy men ran on a treadmill at 70% of maximal oxygen consumption (VO2max) for 1 h after two days of a low-carbohydrate diet. BrAce and blood ketone (acetoacetate (ACAC), beta-hydroxybutyrate (BOHB)) levels were measured at baseline and at different time points of post-exercise. BrAce values were validated against blood ketones and respiratory exchange ratio (RER). Our results showed that BrAce was moderately correlated with BOHB (r = 0.68, p < 0.01), ACAC (r = 0.37, p < 0.01) and blood ketone (r = 0.60, p < 0.01), suggesting that BrAce reflect blood ketone levels, which increase when fat is oxidized. Furthermore, BrAce also negatively correlated with RER (r = 0.67, p < 0.01). In our multiple regression analyses, we found that when BMI and VO2max were added to the prediction model in addition to BrAce, R2 values increased up to 0.972 at rest and 0.917 at 1 h after exercise. In conclusion, BrAce level measurements of our BrAce analyzer reflect blood ketone levels and the device could potentially predict fat oxidation.


Assuntos
Acetona , Testes Respiratórios , Gastos em Saúde , Ácido 3-Hidroxibutírico , Metabolismo Energético , Exercício Físico , Humanos , Masculino , Oxirredução , Consumo de Oxigênio
4.
ACS Appl Mater Interfaces ; 12(16): 18609-18616, 2020 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-32249574

RESUMO

An all-in-one energy harvester module comprising a top piezoelectric layer, a bottom piezoelectric layer, and a middle triboelectric layer was fabricated based on flexible piezoceramic nanofibers to serve as a power source for wearable devices. The top and bottom piezoelectric layers were manufactured by modularizing electrospun piezoceramic nanofibers with an interdigitated electrode, and the energy harvesting characteristics were maximized by laminating the single modules in z-axis array arrangements. The triboelectric layer was manufactured by attaching polydimethylsiloxane on both sides of an electrode layer, and the energy harvesting characteristics were controlled according to the surface roughness of the triboelectric modules. The output voltages of the individual energy harvester modules of the all-in-one module were individually or integrally measured by hand pressing the lower and upper parts of the module. The all-in-one energy harvester module generated a maximum voltage (power) of 253 V (3.8 mW), and the time required to charge a 0.1 µF capacitor to 25 V was 40 s. The results of a simulated energy harvesting experiment conducted on the all-in-one energy harvester module showed that 42 LED bulbs arranged in the shape of the "KICET" logo could be turned on in real time without charging, and a mini fan consuming a power of 3.5 W was operated after charging a 10 µF capacitor for 250 s. This work shows the potential of the all-in-one module as an ecofriendly flexible energy harvester for operating wearable devices.

5.
J Immunol ; 204(9): 2552-2561, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32205425

RESUMO

The adaptive immune function of lymph nodes is dependent on constant recirculation of lymphocytes. In this article, we identify neutrophils present in the lymph node at steady state, exhibiting the same capacity for recirculation. In germ-free mice, neutrophils still recirculate through lymph nodes, and in mice cohoused with wild microbiome mice, the level of neutrophils in lymph nodes increases significantly. We found that at steady state, neutrophils enter the lymph node entirely via L-selectin and actively exit via efferent lymphatics via an S1P dependent mechanism. The small population of neutrophils in the lymph node can act as reconnaissance cells to recruit additional neutrophils in the event of bacterial dissemination to the lymph node. Without these reconnaissance cells, there is a delay in neutrophil recruitment to the lymph node and a reduction in swarm formation following Staphylococcus aureus infection. This ability to recruit additional neutrophils by lymph node neutrophils is initiated by LTB4. This study establishes the capacity of neutrophils to recirculate, much like lymphocytes via L-selectin and high endothelial venules in lymph nodes and demonstrates how the presence of neutrophils at steady state fortifies the lymph node in case of an infection disseminating through lymphatics.


Assuntos
Linfonodos/imunologia , Infiltração de Neutrófilos/imunologia , Neutrófilos/imunologia , Infecções Estafilocócicas/imunologia , Animais , Endotélio/imunologia , Endotélio/microbiologia , Feminino , Selectina L/imunologia , Linfonodos/microbiologia , Vasos Linfáticos/imunologia , Vasos Linfáticos/microbiologia , Linfócitos/imunologia , Linfócitos/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microbiota/imunologia , Receptores de Esfingosina-1-Fosfato/imunologia , Infecções Estafilocócicas/microbiologia , Vênulas/imunologia , Vênulas/microbiologia
6.
Nat Commun ; 11(1): 805, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-32041949

RESUMO

Photolithography is the prevalent microfabrication technology. It needs to meet resolution and yield demands at a cost that makes it economically viable. However, conventional far-field photolithography has reached the diffraction limit, which imposes complex optics and short-wavelength beam source to achieve high resolution at the expense of cost efficiency. Here, we present a cost-effective near-field optical printing approach that uses metal patterns embedded in a flexible elastomer photomask with mechanical robustness. This technique generates sub-diffraction patterns that are smaller than 1/10th of the wavelength of the incoming light. It can be integrated into existing hardware and standard mercury lamp, and used for a variety of surfaces, such as curved, rough and defect surfaces. This method offers a higher resolution than common light-based printing systems, while enabling parallel-writing. We anticipate that it will be widely used in academic and industrial productions.

7.
Soft Robot ; 7(5): 564-573, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31977289

RESUMO

There has been a great deal of interest in designing soft robots that can mimic a human system with haptic and proprioceptive functions. There is now a strong demand for soft robots that can sense their surroundings and functions in harsh environments. This is because the wireless sensing and actuating capabilities of these soft robots are very important for monitoring explosive gases in disaster areas and for moving through contaminated environments. To develop these wireless systems, complex electronic circuits must be integrated with various sensors and actuators. However, the conventional electronic circuits based on silicon are rigid and fragile, which can limit their reliable integration with soft robots for achieving continuous locomotion. In our study, we developed an untethered, soft robotic hand that mimics human fingers. The soft robotic fingers are composed of a thermally responsive elastomer composite that includes capsules of ethanol and liquid metals for its shape deformation through an electrothermal phase transition. And these soft actuators are integrated fully with flexible forms of heaters, with pressure, temperature, and hydrogen gas sensors, and wireless electronic circuits. Entire functions of this soft hand, including the gripping motion of soft robotic fingers and the real-time detections of tactile pressures, temperatures, and hydrogen gas concentrations, are monitored or controlled wirelessly using a smartphone. This wireless sensing and actuating system for somatosensory and respiratory functions of a soft robot provides a promising strategy for next-generation robotics.

8.
ACS Nano ; 13(11): 13317-13324, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31613598

RESUMO

Electronic band engineering is a promising approach to enhance the thermopower of thermoelectric materials. In transition-metal dichalcogenides (TMDCs), this has so far only been achieved using their inherent semiconducting nature. Here, we report the thickness-modulated band engineering of nanosheets based on semimetallic platinum diselenide (PtSe2) resulting in a thermopower enhancement of more than 50 times than that of the bulk. We obtained this by introducing a semimetal to semiconductor (SMSC) transition resulting in the formation of a bandgap. This approach based on semimetallic TMDCs provides potential advantages such as a large variation of transport properties, a decrease of the ambipolar transport effect, and a high carrier density dependence of the transport properties. Our observations suggest that the SMSC transition in TMDCs is a promising and straightforward strategy for the development of two-dimensional nanostructured thermoelectric materials.

9.
Sensors (Basel) ; 19(16)2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31443298

RESUMO

N-containing gaseous compounds, such as trimethylamine (TMA), triethylamine (TEA), ammonia (NH3), nitrogen monoxide (NO), and nitrogen dioxide (NO2) exude irritating odors and are harmful to the human respiratory system at high concentrations. In this study, we investigated the sensing responses of five sensor materials-Al-doped ZnO (AZO) nanoparticles (NPs), Pt-loaded AZO NPs, a Pt-loaded WO3 (Pt-WO3) thin film, an Au-loaded WO3 (Au-WO3) thin film, and N-doped graphene-to the five aforementioned gases at a concentration of 10 parts per million (ppm). The ZnO- and WO3-based materials exhibited n-type semiconducting behavior, and their responses to tertiary amines were significantly higher than those of nitric oxides. The N-doped graphene exhibited p-type semiconducting behavior and responded only to nitric oxides. The Au- and Pt-WO3 thin films exhibited extremely high responses of approximately 100,000 for 10 ppm of triethylamine (TEA) and approximately -2700 for 10 ppm of NO2, respectively. These sensing responses are superior to those of previously reported sensors based on semiconducting metal oxides. On the basis of the sensing response results, we drew radar plots, which indicated that selective pattern recognition could be achieved by using the five sensing materials together. Thus, we demonstrated the possibility to distinguish each type of gas by applying the patterns to recognition techniques.

10.
Sensors (Basel) ; 19(9)2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31035672

RESUMO

Multi-sensor perception systems may have mismatched coordinates between each sensor even if the sensor coordinates are converted to a common coordinate. This discrepancy can be due to the sensor noise, deformation of the sensor mount, and other factors. These mismatched coordinates can seriously affect the estimation of a distant object's position and this error can result in problems with object identification. To overcome these problems, numerous coordinate correction methods have been studied to minimize coordinate mismatching, such as off-line sensor error modeling and real-time error estimation methods. The first approach, off-line sensor error modeling, cannot cope with the occurrence of a mismatched coordinate in real-time. The second approach, using real-time error estimation methods, has high computational complexity due to the singular value decomposition. Therefore, we present a fast online coordinate correction method based on a reduced sensor position error model with dominant parameters and estimate the parameters by using rapid math operations. By applying the fast coordinate correction method, we can reduce the computational effort within the necessary tolerance of the estimation error. By experiments, the computational effort was improved by up to 99.7% compared to the previous study, and regarding the object's radar the identification problems were improved by 94.8%. We conclude that the proposed method provides sufficient correcting performance for autonomous driving applications when the multi-sensor coordinates are mismatched.

11.
ACS Appl Mater Interfaces ; 11(3): 2917-2924, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30580514

RESUMO

Wetting of the liquid metal on the solid electrolyte of a liquid metal battery controls the operating temperature and performance of the battery. Liquid sodium electrodes are particularly attractive because of their low cost, natural abundance, and geological distribution. However, they wet poorly on a solid electrolyte near its melting temperature, limiting their widespread suitability for low-temperature batteries to be used for large-scale energy storage systems. Herein, we develop an isolated metal-island strategy that can improve sodium wetting in sodium-beta alumina batteries that allows operation at lower temperatures. Our results suggest that in situ heat treatment of a solid electrolyte followed by bismuth deposition effectively eliminates oxygen and moisture from the surface of the solid electrolyte, preventing the formation of an oxide layer on the liquid sodium, leading to enhanced wetting. We also show that employing isolated bismuth islands significantly improves cell performance, with cells retaining 94% of their charge after the initial cycle, an improvement over cells without bismuth islands. These results suggest that coating isolated metal islands is a promising and straightforward strategy for the development of low-temperature sodium-ß alumina batteries.

12.
J Nanosci Nanotechnol ; 18(2): 1232-1236, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29448563

RESUMO

In this work, we present the fabrication and characterization of a 2-chloroethyl ethyl sulfide (2-CEES) gas sensor based on ZnO nanoparticles (NPs) synthesized by a hydrothermal method. We confirmed that synthesized ZnO NPs adopt a polycrystalline phase. Partially aggregated ZnO-NPs revealed spherical or ellipsoidal nanocrystalline particles in a size range of 30-50 nm, as observed by field-emission scanning electron microscopy (FE-SEM). The maximum response of the ZnO NPs was 15 at 1 ppm 2-CEES concentration, and a low detection limit of 0.4 ppm was observed at an optimal operating temperature of 250 °C. The lowest response time was 6 s in 20 ppm at 250 °C. The linearity response with correlation coefficient (R2) was 0.9887 at 2-CEE concentrations of 0.4-1 ppm at the operating temperature of 250 °C. The enhanced sensing performance and a decrease in the operating temperature were attributed to a high specific surface area and more active sites in the ZnO NPs after exposure to 2-CEES.

13.
Nanotechnology ; 29(1): 015404, 2018 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-29115283

RESUMO

The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350-450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior. By contrast, the sign of the Seebeck coefficient for Ag nanoparticle-doped RuO2 nanosheets does not change with temperature, indicating that the extra charge carriers from metal nanoparticles promote n-type semiconductor behavior.

14.
J Hazard Mater ; 338: 447-457, 2017 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-28595159

RESUMO

In this report, magnetically recoverable sulfur-doped SnFe2O4/graphene (S-SFO/GR) nanohybrids have been successfully developed via a facile solvothermal method. The characterizations on the structural, morphology, and optical properties of the nanohybrids indicate that S-SFO particles are successfully embedded on the GR nanosheets. The photocatalytic activity has been evaluated by photocatalytic degradation of chlorotetracycline under visible light irradiation. Among the composites with various mass ratios, the quasi-first-order rate constant of the nanohybrids formed with 9wt% S in SFO and 15wt% GR (9S-SFO/GR-15) can reach as high as 1.83min-1, which is much higher than that of SFO (0.68min-1) and SFO/GR (0.91min-1), confirming the important role of S and GR for the photocatalytic process. The combination of the three components of S, SFO, and GR has enhanced the visible light absorption capability and inhibited the recombination of photogenerated electron-hole. The 9S-SFO/GR-15 nanohybrids can be recovered easily by a magnet and reused for five times with remained photocatalytic efficiency about 70%. A possible catalytic mechanism explaining the efficient photocatalytic performances of the prepared nanohybrids has been proposed.

15.
Sci Rep ; 7(1): 3062, 2017 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-28596574

RESUMO

Droplet control through the use of light-induced thermocapillary effects has recently garnered attention due to its non-intrusive and multifunctional nature. An important issue in droplet control is the estimation of the thermocapillary force. The purpose of the present study is to estimate the thermocapillary force and propose empirical equations between the force and simply measurable key parameters such as droplet diameter and power of heat source. In addition, we aim to shift the droplet trajectory and develop an on-demand droplet routing system based on the estimation of the thermocapillary force. We illuminated a continuous phase with a 532 nm laser beam to minimize possible damage or property changes to target molecules contained within droplets. A mixture of light-absorbing material and oleic acid was used for the continuous phase fluid, while deionized water (DI water) was used for the dispersed phase fluid. We proposed empirical equations to estimate the thermocapillary force, which was then applied to precise droplet shifting and routing. We found that the shifting distance was linearly proportional to the thermocapillary force, and that an on-demand droplet routing system resulted in a success rate greater than 95%.

16.
Nanoscale ; 9(21): 7104-7113, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28513639

RESUMO

The enhancement in electrical transport properties of exfoliated individual RuO2 NSs was systemically investigated for their application in flexible electronics and optoelectronics. Decoration of Ag NPs on the surface of the RuO2 NSs provides donor electrons and dramatically increases the electrical conductivity of the monolayer RuO2 NSs by up to 3700%. The n-type doping behavior was confirmed via Hall measurement analysis of the doped RuO2 NSs. The layer number- and temperature-dependence of the conductivity were also investigated. Moreover, carrier concentration and mobility were obtained from Hall measurements, indicating that the undoped RuO2 NSs had ambipolar transport and semi-metallic characteristics. Moreover, the Ag-doped RuO2 NS multilayer films on polycarbonate substrates were demonstrated by the Langmuir-Blodgett assembly methods, showing one-third reduction in the sheet resistance and extraordinarily high bending stability that the change in the resistance was less than 1% over 50 000 cycles.

17.
J Phys Chem Lett ; 8(12): 2597-2601, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28520429

RESUMO

One of the unsolved fundamental issues of graphene is establishing an appropriate way to discern layers of graphene structures. We report a simple methodology to analyze graphene structures using Raman signals in the range of ∼100 to ∼500 cm-1 comprising clear 118 or 175 cm-1 peaks. We demonstrate that the low-energy signals on Raman spectra of plasma-seeded grown graphene sheets originated from nanocurvature (c) of mono- (175 and 325-500 cm-1 signals) (c ≈ 1 nm) and bilayer (118 cm-1 peak) (c ≈ 2 nm) graphene with Raman simulations, based on Raman radial mode (RM) Eigen vectors. Our RM model provides a standard way of identifying and evaluating graphene structures.

18.
Small ; 13(43)2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28524361

RESUMO

Fabrication strategies that pursue "simplicity" for the production process and "functionality" for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper-based pressure sensors are integrated into a fully functional 3D touch-pad device, which is a step toward the realization of omnipresent electronics.

19.
Nanoscale ; 9(2): 923-929, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-28000830

RESUMO

A semimetal to semiconductor transition in low-dimensional Bi nanowires is theoretically predicted based on the quantum confinement effect, which results in the enhancement of the thermoelectric performance. However, this transition has rarely been observed in the transport properties of gate modulation because of there being too few charge carriers induced by a typical electric field effect. In this paper, we report on our observations of the on-off state in a Bi nanowire using a polyethylene oxide/LiClO4 electrolyte gate, which produces a much larger effect than a back-gate. The carrier density of the surface state was found to be consistent with previously reported results. The intrinsic properties of the Bi nanowires, as obtained by temperature- and diameter-dependent gate modulations, are also discussed.

20.
Sci Rep ; 6: 39624, 2016 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-28000780

RESUMO

Over the history of carbon, it is generally acknowledged that Bernal AB stacking of the sp2 carbon layers is the unique crystalline form of graphite. The universal graphite structure is synthesized at 2,600~3,000 °C and exhibits a micro-polycrystalline feature. In this paper, we provide evidence for a metastable form of graphite with an AA' structure. The non-Bernal AA' allotrope of graphite is synthesized by the thermal- and plasma-treatment of graphene nanopowders at ~1,500 °C. The formation of AA' bilayer graphene nuclei facilitates the preferred texture growth and results in single-crystal AA' graphite in the form of nanoribbons (1D) or microplates (2D) of a few nm in thickness. Kinetically controlled AA' graphite exhibits unique nano- and single-crystalline feature and shows quasi-linear behavior near the K-point of the electronic band structure resulting in anomalous optical and acoustic phonon behavior.

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