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1.
Proc Natl Acad Sci U S A ; 121(13): e2317192121, 2024 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-38507451

RESUMO

Photothermal heating and photocatalytic treatment are two solar-driven water processing approaches by harnessing NIR and UV-vis light, respectively, which can fully utilize solar energy if integrated. However, it remains a challenge to achieve high performance in both approaches when integrated in a material due to uncontrollable heat diffusion. Here, we report a demonstration of heat confinement on photothermal sites and fluid cooling on photocatalysis sites at the nanoscale, within a well-designed heat and fluid confinement nanofiber reactor. Photothermal and photocatalytic nanostructures were alternatively aligned in electrospun nanofibers for on-demand nanofluidic thermal management as well as easy folding into 3D structures with enhanced light utilization and mass transfer. Such a design showed simultaneously high photothermal evaporation rate (2.59 kg m-2 h-1, exceeding the limit rate) and efficient photocatalytic upcycling of microplastics pollutant into valued products. Enabled by controlled photothermal heating, the valued main product (i.e., methyl acetate) can be evaporated out with 100% selectivity by in situ separation.

2.
Nat Commun ; 14(1): 2643, 2023 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-37156784

RESUMO

Photoelectrochemical device is a versatile platform for achieving various chemical transformations with solar energy. However, a grand challenge, originating from mass and electron transfer of triphase-reagents/products in gas phase, water/electrolyte/products in liquid phase and catalyst/photoelectrode in solid phase, largely limits its practical application. Here, we report the simulation-guided development of hierarchical triphase diffusion photoelectrodes, to improve mass transfer and ensure electron transfer for photoelectrochemical gas/liquid flow conversion. Semiconductor nanocrystals are controllably integrated within electrospun nanofiber-derived mat, overcoming inherent brittleness of semiconductors. The mechanically strong skeleton of free-standing mat, together with satisfactory photon absorption, electrical conductivity and hierarchical pores, enables the design of triphase diffusion photoelectrodes. Such a design allows photoelectrochemical gas/liquid conversion to be performed continuously in a flow cell. As a proof of concept, 16.6- and 4.0-fold enhancements are achieved for the production rate and product selectivity of methane conversion, respectively, with remarkable durability.

3.
Small ; 19(34): e2300547, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37093186

RESUMO

Sintering is a major concern for the deactivation of supported metals catalysts, which is driven by the force of decreasing the total surface energy of the entire catalytic system. In this work, a double-confinement strategy is demonstrated to stabilize 2.6 nm-Pt clusters against sintering on electrospun CeO2 nanofibers decorated by CeO2 nanocubes (m-CeO2 ). Thermodynamically, with the aid of CeO2 -nanocubes, the intrinsically irregular surface of polycrystalline CeO2 nanofibers becomes smooth, offering adjacent Pt clusters with decreased chemical potential differences on a relatively uniform surface. Kinetically, the Pt clusters are physically restricted on each facet of CeO2 nanocubes in a nanosized region. In situ high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation reveals that the Pt clusters can be stabilized up to 800 °C even in a high density, which is far beyond their Tammann temperature, without observable size growth or migration. Such a sinter-resistant catalytic system is endowed with boosted catalytic activity toward both the hydrogenation of p-nitrophenol after being aged at 500 °C and the sinter-promoting exothermic oxidation reactions (e.g., soot oxidation) at high temperatures over 700 °C. This work offers new opportunities for exploring sinter-resistant nanocatalysts, starting from the rational design of whole catalytic system in terms of thermodynamic and kinetic aspects.

4.
Mater Horiz ; 10(1): 65-74, 2023 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-36477767

RESUMO

TiO2 nanomaterials, especially one-dimensional TiO2 nanofibers fabricated by electrospinning, have received considerable attention in the past two decades, for a variety of basic applications. However, their safe use and easy recycling are still hampered by the inherently subpar mechanical performance. Here, we toughened polycrystalline TiO2 nanofibers by introducing Al3+-species at the very beginning of electrospinning. The resultant long-and-continuous TiO2 nanofibers achieved a Young's modulus of 653.8 MPa, which is ca. 25-fold higher than that of conventional TiO2 nanofibers. Within each nanofiber, amorphous Al2O3-based oxide effectively hindered the coalescence of TiO2 nanocrystals and potentially repaired the surface groves. The solid-state 17O-NMR spectra further revealed the toughening strategy on a molecular scale, where relatively flexible Ti-O-Al bonds replaced rigid O-Ti-O bonds at the interfaces of TiO2 and Al2O3. Moreover, the modified TiO2 nanofibers exhibited superb sinter-resistance, without cracking over 900 °C, which was dynamically monitored by TEM. Therefore, flexible-in-rigid TiO2 fibrous mats can be facilely folded into 3D sponges through origami art. As a potential showcase, the TiO2 sponges were demonstrated as a duarable and renewable filtrator with a high filtration efficiency of 99.97% toward PM2.5 and 99.99% toward PM10 after working for 300 min. This work provides a rational strategy to produce flexible oxide nanofibers and gives an in-depth understanding of the toughening mechanism from the macro-scale to the molecular-scale.


Assuntos
Nanofibras , Nanofibras/química , Titânio/química , Filtração , Óxidos
5.
Nanomaterials (Basel) ; 12(24)2022 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-36558276

RESUMO

In recent years, graphene has shown great application prospects in tunable microwave devices due to its tunable conductivity. However, the electromagnetic (EM) properties of graphene, especially the dynamic tunning characteristics, are largely dependent on experimental results, and thus are unable to be effectively predicted according to growth parameters, which causes great difficulties in the design of graphene-based tunable microwave devices. In this work, we systematically explored the impact of chemical vapor deposition (CVD) parameters on the dynamic tunning range of graphene. Firstly, through improving the existing waveguide method, the dynamic tunning range of graphene can be measured more accurately. Secondly, a direct mathematical model between growth parameters and the tunning range of graphene is established. Through this, one can easily obtain needed growth parameters for the desired tunning range of graphene. As a verification, a frequency tunable absorber prototype is designed and tested. The good agreement between simulation and experimental results shows the reliability of our mathematic model in the rapid design of graphene-based tunable microwave devices.

6.
Light Sci Appl ; 11(1): 307, 2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36280662

RESUMO

Microwave transmission lines in wearable systems are easily damaged after frequent mechanical deformation, posing a severe threat to wireless communication. Here, we report a new strategy to achieve stretchable microwave transmission lines with superior reliability and durability by integrating a self-healable elastomer with serpentine-geometry plasmonic meta-waveguide to support the spoof surface plasmon polariton (SSPP). After mechanical damage, the self-healable elastomer can autonomously repair itself to maintain the electromagnetic performance and mechanical strength. Meanwhile, the specially designed SSPP structure exhibits excellent stability and damage resistance. Even if the self-healing process has not been completed or the eventual repair effect is not ideal, the spoof plasmonic meta-waveguide can still maintain reliable performance. Self-healing material enhances strength and durability, while the SSPP improves stability and gives more tolerance to the self-healing process. Our design coordinates the structural design with material synthesis to maximize the advantages of the SSPP and self-healing material, significantly improving the reliability and durability of stretchable microwave transmission lines. We also perform communication quality experiments to demonstrate the potential of the proposed meta-waveguide as interconnects in future body area network systems.

7.
Biomed Mater ; 17(3)2022 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-35358956

RESUMO

It is very desirable to have good antibacterial properties and mechanical properties at the same time for bone scaffolds. Graphene oxide (GO) can increase the mechanical properties and antibacterial performance, while forsterite (Mg2SiO4) as the matrix can increase forsterite/GO scaffolds' biological activity for bone tissue engineering. Interconnected porous forsterite scaffolds were developed by space holder processes for bone tissue engineering in this research. The forsterite/GO scaffolds had a porosity of 76%-78% with pore size of 300-450 µm. The mechanism of the mechanical strengthening, antibacterial activity, and cellular function of the forsterite/GO scaffold was evaluated. The findings show that the compressive strength of forsterite/1 wt.% GO scaffold (2.4 ± 0.1 MPa) was significantly increased, in comparison to forsterite scaffolds without GO (1.4 ± 0.1 MPa). Validation of the samples' bioactivity was attained by forming a hydroxyapatite layer on the forsterite/GO surface withinin vitroimmersion test. The results of cell viability demonstrated that synthesized forsterite scaffolds with low GO did not show cytotoxicity and enhanced cell proliferation. Antibacterial tests showed that the antibacterial influence of forsterite/GO scaffold was strongly correlated with GO concentration from 0.5 to 2 wt.%. The scaffold encapsulated with 2 wt.% GO had the great antibacterial performance with bacterial inhibition rate around 90%. As results show, the produced forsterite/1 wt.% GO can be an attractive option for bone tissue engineering.


Assuntos
Grafite , Alicerces Teciduais , Antibacterianos/farmacologia , Porosidade , Compostos de Silício , Engenharia Tecidual/métodos
8.
Nanoscale ; 13(48): 20564-20575, 2021 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-34870662

RESUMO

Airborne particulate matter (PM) primarily resulting from fossil fuel burning is an increasingly global issue. In this work, an intrinsically fragile TiO2 nanofibrous mat was facilely engineered with good structural integrity, flexibility, foldability, and high-temperature resistance (~1300 °C), by suppressing the sintering (i.e., growth) of nanocrystallites in each single nanofiber. Such functionalization enables self-regenerative air filtration for PM capture and in situ catalytic elimination in a "one-stone-two-birds" approach. Finite element analysis simulation revealed the retained nanopores in each anti-sintering nanofiber could facilitate the air flow during filtration. Without any chemical or physical modification, this self-standing and lightweight (7.1 g m-2) fibrous mat showed 96.05% filtration efficiency for 3-5 µm NaCl particles, with a low pressure drop of only 18 Pa and high quality factor of 0.179 Pa-1 under an airflow velocity of 32 L min-1. By utilizing its photocatalytic attribute, the nanofibrous mat in situ eliminated the captured particles from incense burning under one Sun irradiation in 4 h, and thereby spontaneously regenerated in an easy manner. The straightforward grafting of Au nanoparticles onto nanofibers could enable a quick degradation toward cigarette smoke, mainly due to the photothermally elevated local temperature by Au around the reactive sites. The plasmonic fibrous mat kept a high and stable filtration efficiency of PM0.3, PM2.5, and PM10 over 98.62%, 99.76%, and 99.99% during an outdoor long-term filtration test for 12 h under sunlight irradiation (Nanjing, China, September, 26th, 2020, 7:30 to 19:30). This work provides a solution for solving the airborne pollution from its source, prolonging the lifetime of the filter, and avoiding the risk of producing secondary pollution.

9.
Polymers (Basel) ; 13(11)2021 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-34199643

RESUMO

The massive plastic production worldwide leads to a global concern for the pollution made by the plastic wastes and the environmental issues associated with them. One of the best solutions is replacing the fossil-based plastics with bioplastics. Bioplastics such as polylactic acid (PLA) are biodegradable materials with less greenhouse gas (GHG) emissions. PLA is a biopolymer produced from natural resources with good mechanical and chemical properties, therefore, it is used widely in packaging, agriculture, and biomedical industries. PLA products mostly end up in landfills or composting. In this review paper, the existing life cycle assessments (LCA) for PLA were comprehensively reviewed and classified. According to the LCAs, the energy and materials used in the whole life cycle of PLA were reported. Finally, the GHG emissions of PLA in each stage of its life cycle, including feedstock acquisition and conversion, manufacturing of PLA products, the PLA applications, and the end of life (EoL) options, were described. The most energy-intensive stage in the life cycle of PLA is its conversion. By optimizing the conversion process of PLA, it is possible to make it a low-carbon material with less dependence on energy sources.

10.
ACS Appl Mater Interfaces ; 13(29): 34157-34167, 2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34255477

RESUMO

Overdischarge is a severe safety issue that can induce severe mechanical failure of electrode materials in lithium-ion batteries. A considerable volume change of silicon-based composite anodes undoubtedly further aggravates the mechanical failure. However, the mechanical failure mechanism of silicon-based composite anodes under overdischarging conditions still lacks in-depth understanding despite many efforts paid under normal charging conditions. Herein, we have modeled and tracked the mechanical failure evolution of silicon/carbon nanofibers, a typical silicon-based anode, under overdischarging conditions based on the finite element simulation, with derived optimization strategies of optimal Young's modulus and stable microstructure. The severe contact damage between silicon nanoparticles and carbon nanofibers, which causes larger shedding and breakage risks, has been found to contribute to mechanical failure. To improve the electrode stability, an optimal Young's modulus interval ranging from ∼75 to ∼150 GPa is found. Furthermore, increasing the embedding depth of silicon nanoparticles in carbon nanofibers has proven to be an effective strategy for improving electrochemical stability due to the faster lithium salt diffusion and more uniform current density distribution, which was further verified by the experimental capacity retention ratio of carbon-coated silicon and silicon/carbon nanofibers (84 vs 75% after 100 cycles). Our results provide meaningful insights into the mechanical failure of silicon-based composite anodes during overdischarging, giving reasonable guidance for electrode safety designs and performance optimization.

11.
ACS Appl Mater Interfaces ; 13(22): 26561-26572, 2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-34038638

RESUMO

This work demonstrates a facile fabrication of stimulus-responsive, periodically wrinkled graphene sheets on grooved microfiber arrays with fast and reversible shape change, multiresponsiveness, and programmable deformation, with the aid of finite element analysis (FEA). The cellulose acetate (CA) microfibers, endowing responsiveness to humidity and solvents, are designed to grooved shape and assembled into a well-aligned fibrous mat by electrospinning. Under the guidance of FEA simulation, the stiff reduced graphene oxide (RGO) sheets, serving as a photoresponsive component, could ably bind on grooved CA microfibers with favorable interlocked interfacial-structure. Through simple direct-writing and hot-pressing, the grooved CA arrays interlocked the conformal RGO sheets by water-induced self-clamping, and enabled the generation of periodic wrinkles within RGO sheets to maximize interfacial areas. By simply adjusting the orientation of written RGO patterns relative to uniaxial CA microfibers, programmed and omnidirectional shape-shifting were obtained to minimize strain energy, consisting with the dynamic deformation process simulated by FEA. Upon remote light or contactless humidity stimuli, the RGO/CA mat shows a rapid response (≤1 s), large amplitude (angle change ≥150°, 1.62 cm-1), sophisticated 3D motions, and lifts objects that weigh 12.7-times its own weight up to over 1/3 of own height within 1 s. After loading catalytical nanoparticles, the RGO/CA mat could rapidly move to the targeted position by continuous crawling even on a slippery surface, and served as a microchannel reactor to trigger a reaction in built-in microchannels with suppressing catalyst leaching while accelerating reaction kinetics by both nanoconfinement and photothermal effect.

12.
Nanoscale ; 12(37): 19104-19111, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32691815

RESUMO

Both oxygen vacancies and surface chemistry can affect the enzyme-like catalytic activities of CeO2-based nanozymes. However, the mechanism of the enzyme-mimetic process is not yet clearly elucidated, which is of great importance to guide the synthesis of high-performance nanozymes with desirable properties. Herein, we report a facile one-pot solvothermal method for the preparation of polyvinylpyrrolidone (PVP)-capped CeO2 nanoflowers with adjustable oxygen vacancies by changing appropriate solvothermal reaction parameters. Oxygen vacancies effectively increase under a higher precursor concentration, extended solvothermal time, and proper reaction temperature. The maximum content of surface Ce(iii) cations is up to 50% for 31.1 nm CeO2 nanoflowers, which exhibit 0.07 mM apparent Michaelis constant towards 3,3',5,5'-tetramethylbenanozymeidine and show a higher binding affinity than the other CeO2-based catalysts. Theoretical results indicate that the synergy between PVP and oxygen vacancies can significantly promote the adsorption of O2 and TMB on CeO2, which directly enhances the oxidase-mimetic activity of flower-like CeO2 nanozymes. This work can shed light on a new perspective on the enzyme-like performance promotion of CeO2-based catalysts and surface engineering of nanozymes.

13.
Chem Rev ; 119(8): 5298-5415, 2019 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-30916938

RESUMO

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.


Assuntos
Técnicas Eletroquímicas/métodos , Nanofibras/química , Animais , Humanos , Nanotecnologia/métodos
14.
Nanotechnology ; 30(4): 045602, 2019 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-30479314

RESUMO

Recently, there has been strong interest in flexible and wearable electronics to meet the technological demands of modern society. Environmentally-friendly and scalable electronic textiles is a key area that is still significantly underdeveloped. Here, we describe a novel strain sensor composed of aligned cellulose acetate (CA) nanofibers with belt-like morphology and a reduced graphene oxide (RGO) layer. The unique spatial alignment, microstructure and wettability of CA nanofibrous membranes facilitate their close contact with deposited GO colloids. After a portable and fast hot-press process within 700 s at 150 °C, the GO on CA membrane can be facilely reduced to a conductive RGO layer. Moreover, the connection among contiguous CA nanofibers and the interaction between the GO and CA substrate were both highly enhanced, resulting in superior mechanical strength with Young's modulus of 1.3 GPa and small sheet resistance lower than 10 kΩ. Therefore, the conductive RGO/CA membrane was successfully utilized as a strain sensor in a broad deformation range and with versatile deformation types. Moreover, the distinctive mechanical strength under different stretch angles endowed the well-aligned RGO/CA film with intriguing sensitivity against stress direction. Such a cost-effective and environmentally-friendly method can be easily extended to the scalable production of graphene-based flexible electronic textiles.

15.
Nanotechnology ; 29(46): 465704, 2018 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-30160242

RESUMO

Iron oxide nanoparticles (NPs) possessing peroxidase-like catalytic activity have been widely explored in recent decades, owing to their high stability against harsh conditions, low cost, flexibility in structure design and composition, adjustable activities and excellent biocompatibility in comparison with natural enzymes. Recently, a lot of great achievements have been made in this field of iron oxide nanozymes, however, this research has now reached a bottleneck in that the maximum activity enhancement is difficult to achieve via a material design. Hence, in this work, visible light was introduced to improve the peroxidase-like activity of Fe2O3 NPs synthesized via a combination of electrospinning technology and hydrothermal reaction. Our results showed that with the assistance of visible light, Fe2O3 NPs exhibited at least 2.2-fold higher peroxidase activity than those tested under darkness, confirming the superiorly visible light promoted peroxidase-like catalytic activity of Fe2O3 NPs. Furthermore, the affinity and maximum reaction velocity of Fe2O3 nanoflowers (bandgap = 1.78 eV) towards 3,3',5,5'-tetramethylbenanozymeidine (TMB) were at least over 3.7 and 4.3 times greater than in Fe2O3 nanocubes (bandgap = 2.08 eV), suggesting that the reaction performance of semiconductors could be controlled by proper adjustment of the bandgap. Moreover, the Fe2O3 NPs were also successfully utilized to detect glucose. Herein, we believe that the present work exhibits a fascinating perspective for peroxidase-like catalytic fields.


Assuntos
Compostos Férricos/química , Compostos Férricos/metabolismo , Luz , Nanopartículas/química , Nanopartículas/metabolismo , Peroxidases/metabolismo , Catálise , Colorimetria , Glucose/análise , Peróxido de Hidrogênio/análise , Concentração de Íons de Hidrogênio , Nanopartículas/ultraestrutura , Oxirredução , Peroxidases/química
16.
Nanotechnology ; 29(34): 345607, 2018 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-29920185

RESUMO

Developing a facile strategy to synthesize template-free TiO2 membrane with stable super-hydrophilic surface is still a daunting challenge. In this work, super-hydrophilicity (close to 0°) and underwater super-oleophobicity (165°) have been successfully demonstrated on a hierarchical Al2O3/TiO2 membrane, which is prepared via a facile electrospinning method followed by simple calcination in air. The precisely-tuned Al2O3 heterojunctions grew in situ and dispersed uniformly on the TiO2 surface, resulting in an 'island in the sea' configuration. Such a unique feature allows not only achieving super-hydrophilicity by maximizing the surface roughness and enhancing the hydrogen bonding, but also improving the adsorption capacity toward different toxic dyes utilizing the abundant adsorption sites protected by the hierarchical nanostructure during sintering. The new Al2O3/TiO2 nanofibrous membrane can serve as a novel filter for gravity driven oil/water separation along with dye removal, achieving 97.7% of oil/water separation efficiency and 98% of dye capture, thanks to their superb wettability and the sophisticated adsorptive performance. Our presented fabrication strategy can be extended to a wide range of ceramic materials and inspires their advanced applications in water purification under harsh liquid-phase environments.

17.
Chem Soc Rev ; 47(12): 4314-4331, 2018 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-29745393

RESUMO

Catalyst sintering, a main cause of the loss of catalytic activity and/or selectivity at high reaction temperatures, is a major concern and grand challenge in the general area of heterogeneous catalysis. Although all heterogeneous catalysts are inevitably subjected to sintering during their operation, the immediate and drastic consequences can be mitigated by carefully engineering the catalytic particles and their interactions with the supports. In this tutorial review, we highlight recent progress in understanding the physical chemistry and materials science involved in sintering, including the discussion of advanced techniques, such as in situ microscopy and spectroscopy, for investigating the sintering process and its rate. We also discuss strategies for the design and rational fabrication of sinter-resistant catalysts. Finally, we showcase recent success in improving the thermal stability and thus sinter resistance of supported catalytic systems.

18.
Nanotechnology ; 29(24): 245703, 2018 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-29581413

RESUMO

In this work, the rationally-designed sharp corners on Au nanorods tremendously improved the catalytic activity, particularly in the presence of visible light irradiation, towards the hydrogenation of 4-nitrophenol to 4-aminophenol. A strikingly increased rate constant of 50.6 g-1 s-1 L was achieved in M-Au-3, which was 41.8 times higher than that of parent Au nanorods under dark conditions. The enhanced activities were proportional to the extent of the protruding sharp corners. Furthermore, remarkably enhanced activities were achieved in novel ternary Au/RGO/TiO2 sheets, which were endowed with a 52.0 times higher rate constant than that of straight Au nanorods. These remarkably enhanced activities were even higher than those of previously reported 3-5 nm Au and 3 nm Pt nanoparticles. It was systematically observed that there are three aspects to the synergistic effects between Au and RGO sheets: (i) electron transfer from RGO to Au, (ii) a high concentration of p-nitrophenol close to dumbbell-like Au nanorods on RGO sheets, and (iii) increased local reaction temperature from the photothermal effect of both dumbbell-like Au nanorods and RGO sheets.

19.
Nanotechnology ; 2018 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-29384495

RESUMO

Gold nanoparticles (Au NPs) have attracted remarkable research interests in heterogeneous catalysis due to their unique physical and chemical properties. However, only small-size Au NPs (<7 nm) exhibit promising catalytic activity. In this work, dumbbell-like Au NPs (D-Au NPs) with average size of 37 × 11 nm were prepared by a secondary seed-mediated growth method to serve as novel photocatalyst for ammonia borane (AB) hydrolysis in the solution with specific pH value. Our results demonstrate that ⅰ) the strengthened LSPR compensation effect could effectively remedy the loss of catalytic activity resulting from the size enlarging of D-Au NPs, proven by that the heating power of a single Au nanoparticle (Ps) and turnover frequency of AB molecules within 10 minutes of D-Au NPs are 52.5 and 3.89 times higher than that of spherical Au NPs; ⅱ) the extinction coefficient and Ps of D-Au NPs are almost 2.72 and 2.42 times as high as that of rod-like Au NPs, demonstrating the promoting structure-property relationship of dumbbell-like structure.; ⅲ) when the pH value of AB solution was lower than 6.0, the hydrolysis rate was highly promoted, indicating that H+ ions play an active role in the hydrolysis process. This work greatly extends the application of noble metals and provides a new insight into AB hydrolysis.

20.
ACS Appl Mater Interfaces ; 9(25): 21258-21266, 2017 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-28575576

RESUMO

Recently, hollow nanofibers could be fabricated by coaxis electrospinning method or template method. However, they are limited to applications because of the hardship in actual preparation. In this work, hollow γ-Al2O3 nanofibers with loofah-like skins were first fabricated by using a single spinneret during electrospinning. These intriguing nanofibers were explored as new Pt supports with excellently sinter-resistant performance up to 500 °C, attributed to the unique loofah-like surface of γ-Al2O3 nanofibers and the strong metal-support interactions between Pt and γ-Al2O3. When applied in the catalytic reduction of p-nitrophenol, the Pt/γ-Al2O3 calcined at 500 °C exhibited 4-times higher reaction rate constant (6.8 s-1·mg-1) over free Pt nanocrystals.

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