Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 149
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-32023031

RESUMO

A hierarchical architecture composed of nitrogen (N)-rich carbon@graphitic carbon-coated ZnO nanowire arrays on a graphene fiber (ZnO@C/GF) was fabricated by direct growth of a ZnO@zeolitic imidazolate framework-8 (ZIF-8) core-shell nanowire array on a GF followed by annealing and used as a microelectrode for detection of 2,4,6-trinitrotoluene (TNT). In such a design, ZnO accumulated TNT through a strong nitroxide-zinc interaction and ZIF-8 served as the precursor of the N-rich carbon@graphitic carbon layer that seamlessly connected ZnO with the GF to improve the poor conductivity of ZnO, thus enhancing the sensitivity of the ZnO@C/GF microelectrode. The constructed hierarchical hybrid fiber microsensor exhibited a wide linear response to TNT in a concentration range of 0.1-32.2 µM with a low detection limit of 3.3 nM. This ZnO@C/GF microelectrode was further successfully applied to the detection of TNT in lake and tap water, indicating its promise as a portable sensor for the electrochemical detection of explosive compounds.

2.
Phys Chem Chem Phys ; 22(5): 3112-3121, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31967127

RESUMO

The presence of unpaired electrons (radicals) due to structural defects is believed to contribute to the catalytic reactivity of carbon materials. Graphite oxide and graphene oxide (GO) consist of significant structural defects and hence are considered more reactive than graphite and graphene. However, the relationship between their radical content/reactivity and their physical and chemical structures remains unknown, which limits the fabrication of high efficiency carbon-based catalysts. In this work, we progressively oxidize graphite to achieve graphite oxide and GO with different levels of oxidation and different sizes. It is observed that a maximal radical content can be achieved on graphite oxide with a C/O ratio of ca. 3.0 and a thickness of around 50 nm. Such a graphite oxide contains about 45% of π bonds and 38% of oxygenated bonds, respectively. Thinner or thicker sheets have lower radical contents due to over or insufficient oxidation, respectively. Single GO sheets with high radical contents can only be produced through a combination of oxidation and reduction. The catalytic activity of the graphite/graphene oxide for phenol degradation was found to be linearly correlated to their radical contents. The observations are significant for the advancement of carbon-based metal-free catalysis.

3.
Artigo em Inglês | MEDLINE | ID: mdl-31990516

RESUMO

Blood-contacting medical devices that directly inhibit thrombosis and bacterial infection without using dangerous anticoagulant and antibacterial drugs can save countless lives but have proved extremely challenging. Here, a useful methodology is proposed that employs temporally shaped femtosecond laser ablation combined with fluorination to fabricate multifunctional three-dimensional (3D) micro-nanostructures with excellent hemocompatibility, zero cytotoxicity, outstanding biocompatibility, bacterial infection prevention, and long-term effectiveness on NiTi alloys. These multifunctional 3D micro-nanostructures present 0.1% hemolysis ratio and almost no platelet adhesion and activation, repel blood to inhibit blood coagulation in vitro, maintain 100% cell viability, and have exceptional stability over 6 months. Moreover, the multifunctional 3D micro-nanostructures simultaneously suppress bacterial colonization to form biofilm and kill 100% colonized Pseudomonas aeruginosa (P. aeruginosa) and 95.6% colonized Staphylococcus aureus (S. aureus) after 24 h of incubation, and bacterial residues can be easily removed. The fabrication method in this work has the advantages of simple processing, high efficiency, high quality, and high repeatability, and the new multifunctional 3D micro-nanostructures can effectively prevent thrombosis and bacterial infection, which can be widely applied to various clinical needs such as biomedical devices and implants.

4.
Artigo em Inglês | MEDLINE | ID: mdl-31922711

RESUMO

In this work, a new type of hybrid energy storage device is constructed by combining the zinc-ion supercapacitor and zinc-air battery in mild electrolyte. Reduced graphene oxide with rich defects, large surface area, and abundant oxygen-containing functional groups is used as active material, which exhibits two kinds of charge storage mechanisms of capacitor and battery simultaneously. Apart from the physical adsorption/desorption of anions on the surface of graphene, the zinc ions in electrolyte will be electrochemically adsorbed/desorbed onto the oxygen-containing groups of graphene during the charge/discharge process, contributing extra capacitance to the device. Moreover, the defects in graphene will further improve the electrochemical performance of the energy storage device via catalyzing the oxygen reduction reaction with exposure to air. Consequently, the synergistic effect leads to a record high capacitance of 370.8 F g-1 at a current density of 0.1 A g-1, which is higher than that of zinc-ion supercapacitors reported previously. Furthermore, the hybrid device exhibits a superior cycling stability with 94.5% capacitance retention even after 10000 charge/discharge cycles at a high current density of 5 A g-1. Interestingly, the developed hybrid device can be self-charging automatically after the power is exhausted in the ambient atmosphere. Other electrode materials, such as carbon nanotube paper, are also used to build a hybrid device to verify the feasibility of this strategy. This facile, green, and convenient strategy provides new insight for developing a high performance storage device, showing great application prospect in other hybrid energy storage devices in mild electrolyte.

5.
Adv Mater ; 32(6): e1907005, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31850657

RESUMO

Microsized supercapacitors (mSCs) with small volume, rapid charge-discharge rate, and ultralong cyclic lifetime are urgently needed to meet the demand of miniaturized portable electronic devices. A versatile self-shrinkage assembling (SSA) strategy to directly construct the compact mSCs (CmSCs) from hydrogels of reduced graphene oxide is reported. A single CmSC is only 0.0023 cm3 in volume, which is significantly smaller than most reported mSCs in fiber/yarn and planar interdigital forms. It exhibits a high capacitance of up to 68.3 F cm-3 and a superior cycling stability with 98% capacitance retention after 25 000 cycles. Most importantly, the SSA technique enables the CmSC as the building block to realize arbitrary, programmable, and multi-dimensional integration for adaptable and complicated power systems. By design on mortise and tenon joint connection, autologous integrated 3D interdigital CmSCs are fabricated in a self-holding-on manner, which thus dramatically reduces the whole device volume to achieve the high-performance capacitive behavior. Consequently, the SSA technique offers a universal and versatile approach for large-scale on-demand integration of mSCs as flexible and transformable power sources.

6.
Adv Mater ; 32(6): e1905875, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31856369

RESUMO

The huge amount of moisture in the air is an unexplored and overlooked water resource in nature, which can be useful to solve the worldwide water shortage. However, direct water condensation from natural or even hazy air is always inefficient and inevitably contaminated by numerous impurities of dust, toxic gas, and microorganisms. In this regard, a drinkable and clean water harvester from complex contaminated air with a wide humidity range based on porous sodium polyacrylate/graphene framework (PGF), which can actively sorb moisture from common or even smoggy environments, efficiently grabs impurities, and then releases clean water with a high rejection rate of impurities under solar irradiation, is proposed. This PGF shows a superhigh equilibrium uptake of 5.20 g of water per gram of PGF at a relative humidity (RH) of 100% and 0.14 g g-1 at a low RH of 15%. The rejection rate of impurities is up to 97% for the collected clean water. Moreover, a water harvesting system is established to produce over 25 L clean water per kilogram of PGF one day, enough to meet several people's drinking water demand. This work provides a new strategy for effective production of clean water from the atmosphere of practical significance.

7.
ChemSusChem ; 2019 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-31837120

RESUMO

Rapid development of portable and wearable electronic devices has triggered the increased research interest of small-scale power sources, especially for the micro-supercapacitor (MSC) because of its high power density, long service life and fast charging and discharging rate. Graphene, as an ideal two-dimensional energy storage electrode material with good conductivity, high quantum capacitance, and large specific surface area, can be used as building block for multi-dimensional architecture for MSC. Much efforts have been devoted to construct structures of different dimensions for the advanced graphene-based MSCs (GMSC). In this review, we summarize the recent progress of graphene-based macroscopic assemblies in MSCs, including 1D fiber GMSCs, 2D planar GMSCs and 3D in-plane or stacked GMSCs, and discuss the relationship between the structures and applications of the devices. In addition, future prospects and challenges in the MSCs are also discussed.

8.
Front Chem ; 7: 725, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31781535

RESUMO

Benefiting from unique planar structure, high flexibility, splendid thermal, and electric properties; graphene as a crucial component has been widely applied into smart materials and multi-stimulus responsive actuators. Moreover, graphene with easy processing and modification features can be decorated with various functional groups through covalent or non-covalent bonds, which is promising in the conversion of environmental energy from single and/or multi-stimuli, to mechanical energy. In this review, we present the actuating behaviors of graphene, regulated by chemical bonds or intermolecular forces under multi-stimuli and summarize the recent advances on account of the unique nanostructures in various actuation circumstances such as thermal, humidity, electrochemical, electro-/photo-thermal, and other stimuli.

9.
Microsyst Nanoeng ; 5: 48, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31645998

RESUMO

Raman spectroscopy plays a crucial role in biochemical analysis. Recently, superhydrophobic surface-enhanced Raman scattering (SERS) substrates have enhanced detection limits by concentrating target molecules into small areas. However, due to the wet transition phenomenon, further reduction of the droplet contact area is prevented, and the detection limit is restricted. This paper proposes a simple method involving femtosecond laser-induced forward transfer for preparing a hybrid superhydrophilic-superhydrophobic SERS (HS-SERS) substrate by introducing a superhydrophilic pattern to promote the target molecules to concentrate on it for ultratrace detection. Furthermore, the HS-SERS substrate is heated to promote a smaller concentrated area. The water vapor film formed by the contact of the solution with the substrate overcomes droplet collapse, and the target molecules are completely concentrated into the superhydrophilic region without loss during evaporation. Finally, the concentrated region is successfully reduced, and the detection limit is enhanced. The HS-SERS substrate achieved a final contact area of 0.013 mm2, a 12.1-fold decrease from the unheated case. The reduction of the contact area led to a detection limit concentration as low as 10-16 M for a Rhodamine 6G solution. In addition, the HS-SERS substrate accurately controlled the size of the concentrated areas through the superhydrophilic pattern, which can be attributed to the favorable repeatability of the droplet concentration results. In addition, the preparation method is flexible and has the potential for fluid mixing, fluid transport, and biochemical sensors, etc.

10.
Angew Chem Int Ed Engl ; 58(52): 19041-19046, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31605566

RESUMO

Solar-driven interfacial water evaporation yield is severely limited by the low efficiency of solar thermal energy. Herein, the injection control technique (ICT) achieves a capillary water state in rGO foam and effectively adjusts the water motion mode therein. Forming an appropriate amount of capillary water in the 3D graphene foam can greatly increase the vapor escape channel, by ensuring that the micrometer-sized pore channels do not become completely blocked by water and by exposing as much evaporation area as possible while preventing solar heat from being used to heat excess water. The rate of solar steam generation can reach up to 2.40 kg m-2 h-1 under solar illumination of 1 kW m-2 , among the best values reported. In addition, solar thermal efficiency approaching 100 % is achieved. This work enhances solar water-evaporation performance and promotes the application of solar-driven evaporation systems made of carbon-based materials.

11.
Nanoscale ; 11(48): 23083-23091, 2019 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-31478548

RESUMO

The exploration of green and clean energy could solve the increasingly serious problems of environmental pollution and energy crisis on the Earth. Moist air is ubiquitous around the world, which particulalrly has huge chemical potential energy because of the gaseous state of the water molecules. Recently, our group demonstrated direct electricity generation by the interactions between moisture and various functional materials, which opened a window for the utilization of moisture power. This has led to an upsurge in studies on moist-electric generation (MEG). In this minireview, we provide a brief and systematic discussion on MEG from its working mechanism to practical applications and, the recent progress in advanced materials. The current challenges and the potential trends in MEG are also outlined to guide the design and synthesis of high-performance MEG devices in the future.

12.
ACS Appl Mater Interfaces ; 11(34): 30927-30935, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31379149

RESUMO

Spontaneous electricity generation through water evaporation is becoming a hot research area. However, low power output, limited material availability, and unscalable fabrication largely hinder its wide applications. Here, we report scalable painting and blade coating approaches for the mass production of flexible hydroelectric films (HEFs) based on solid oxides (e.g., Al2O3), which are of tolerance to mechanical deformation and are compatible with three-dimensional diverse configuration. The electricity power is generated continuously and can last for more than 10 days in ambient conditions. A single HEF unit is capable of supplying an output voltage of more than 2.5 V and even up to 4.5 V at specific conditions. The accumulative energy output can be tuned conveniently by means of series/parallel connections or size control to meet the practical needs of commercial electronics. A family of solid oxides has been verified to have the ability for water evaporation-induced electricity generation, which offers considerable room for the development of high-performance energy-supplying devices.

13.
J Mater Chem B ; 7(35): 5291-5295, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31464334

RESUMO

A novel nitrogen-rich-carbon-coated ZIF-67 embedded three-dimensional-graphene (ZIF-67/NC/3DG) fiber was fabricated via a facile one-pot electrodeposition self-assembly method, and used as a prominent electrode for the non-enzymatic detection of adrenaline (Ad). In this design, the prepared ZIF-67 adsorbs Ad through hydrogen bonding and electrostatic interaction, while polypyrrole functions as the precursor of the conductive NC that seamlessly connects ZIF-67 with the 3DG fiber electrode to ameliorate the poor conductivity of the ZIF-67 moiety and thus improve the sensitivity of the ZIF-67/NC/3DG fiber electrode for detecting Ad. The constructed fiber sensor shows a double linear response over the Ad concentration range of 0.06-95 µM with a high sensitivity of 44.6 mA mM-1 cm-2 and 95.0-5900 µM with a good sensitivity of 11.0 mA mM-1 cm-2, giving a low detection limit of 0.02 µM and excellent repeatability. The ZIF-67/NC/3DG fiber electrode was further successfully applied for the determination of Ad in a real sample of human serum, indicating that this fiber electrode is a promising miniaturized sensor for electrochemical analysis.

14.
Adv Mater ; : e1901979, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31334581

RESUMO

Graphene-based fibers (GBFs) are macroscopic 1D assemblies formed by using microscopic 2D graphene sheets as building blocks. Their unique structure exhibits the same merits as graphene such as low weight, high specific surface area, excellent mechanical/electrical properties, and ease of functionalization. Furthermore, the fibrous nature of GBFs is intrinsically compatible with existing textile technologies, making them suitable for applications in flexible and wearable electronics. Recently, novel synthetic methods have endowed GBFs with new structures and functions, further improving their mechanical and electrical properties. These improvements have rapidly bridged the gaps between laboratory demonstrations and real-life applications in fiber-shaped batteries, supercapacitors, and electrochemical sensors. Recent advances in the fabrication, optimization, and application of GBFs are systematically reviewed and a perspective on their future development is given.

15.
ACS Nano ; 13(8): 9161-9170, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31314490

RESUMO

As an emerging type of electrochemical energy storage devices, sodium-ion capacitors (SICs) are potentially capable of high energy density and high power density, as well as low cost and long lifespan. Unfortunately, the lack of high-performance capacitive cathodes that can fully couple with the well-developed battery-type anodes severely restricts the further development of SICs. Here, we develop a compact yet highly ordered graphene solid (HOGS), which combines the merits of high density and high porosity and, more attractively, possesses a highly ordered lamellar texture with low pore tortuosity. As the capacitive cathode of SICs,  HOGS delivers a record-high volumetric capacity (303 F cm-3 or 219 mA h cm-3 at 0.05 A g-1), a superior rate capability (185 F cm-3 or 139 mA h cm-3 even at 10 A g-1), and an outstanding cycling stability (over 80% after 10 000 cycles). The material design and construction strategies reported here can be easily extended to other metal-ion-based energy storage technologies, exhibiting universal potentials in compact electrochemical energy storage systems.

16.
Nat Commun ; 10(1): 2855, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31253802

RESUMO

Filtering capacitor is a necessary component in the modern electronic circuit. Traditional filtering capacitor is often limited by its bulky and rigid configuration and narrow workable scope of applications. Here, an aqueous hybrid electrochemical capacitor is developed for alternating current line filtering with an applicable wide frequency range from 1 to 10,000 Hz. This capacitor possesses an areal specific energy density of 438 µF V2 cm-2 at 120 Hz, which to the best of our knowledge is record high among aqueous electrochemical capacitors reported so far. It can convert arbitrary alternating current waveforms and even noises to straight signals. After integration of capacitor units, a workable voltage up to hundreds of volts (e.g., 200 V) could be achieved without sacrificing its filtering capability. The integrated features of wide frequency range and high workable voltage for this capacitor present promise for multi-scenario and applicable filtering capacitors of practical importance.

17.
ACS Appl Mater Interfaces ; 11(24): 21822-21829, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31119931

RESUMO

Production or elimination of highly reactive oxygen species is critical in antioxidant, photodynamic, therapeutic, and antibacterial applications. Recent studies have demonstrated that graphene quantum dots (GQDs) possess anti- and pro-oxidant properties simultaneously. However, their efficiency is low. Here, we report chlorine-doped GQDs (Cl-GQDs) with a tunable Cl doping amount and improved anti- and pro-oxidant activities. The scavenging performance and the free radical-produced efficiency of Cl-GQDs are about 7-fold and 3-fold, respectively, higher than those of the undoped GQDs. Meanwhile, Cl-GQDs are considered to be promising for antibacterial applications because of their enhanced singlet oxygen generating ability. We hope that this study could provide a new strategy to develop nanomaterials for application in the anti- and pro-oxidant field.

18.
ACS Nano ; 13(7): 7463-7470, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31136711

RESUMO

The construction of multidimensional, diversified microsupercapacitors (MSC) is urgently needed for fast-changing flexible and wearable microelectronics, which still meets the challenges of tedious construction and difficult integration. Herein, a laser direct writing strategy has been developed for the one-step preparation of multiscale MSCs from editable macro-supercapacitors. The microstructured supercapacitors with predefined multiscale shapes not only maintain the high capacitance performance and stability but also display the tensile properties in arbitrary direction. The heat-treated ion liquid-modified reduced graphene oxide guarantees the thermal stability of an electrode material during laser cutting, and its high ion-accessible surface area improves the capacitance performance of the supercapacitor. The as-fabricated MSC demonstrates a wide voltage window (0-3 V), high areal specific capacitance (27.4 mF cm-2), and high energy density (32.1 µW h cm-2), which are far higher than those of most reported articles. Notably, the editable supercapacitors can imitate the stereo paper cutting to achieve an arbitrary one-dimensional to three-dimensional configuration, promising for various portable, stretchable, and wearable devices.

19.
Nat Commun ; 10(1): 1512, 2019 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-30944322

RESUMO

Natural vascular plants leaves rely on differences in osmotic pressure, transpiration and guttation to produce tons of clean water, powered by sunlight. Inspired by this, we report a sunlight-driven purifier for high-efficiency water purification and production. This sunlight-driven purifier is characterized by a negative temperature response poly(N-isopropylacrylamide) hydrogel (PN) anchored onto a superhydrophilic melamine foam skeleton, and a layer of PNIPAm modified graphene (PG) filter membrane coated outside. Molecular dynamics simulation and experimental results show that the superhydrophilicity of the relatively rigid melamine skeleton significantly accelerates the swelling/deswelling rate of the PNPG-F purifier. Under one sun, this rational engineered structure offers a collection of 4.2 kg m-2 h-1 and an ionic rejection of > 99% for a single PNPG-F from brine feed via the cooperation of transpiration and guttation. We envision that such a high-efficiency sunlight driven system could have great potential applications in diverse water treatments.

20.
Chem Sci ; 10(4): 1244-1253, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30774925

RESUMO

The excellent solution-processability of graphene oxide (GO) has provided a collection of strategies for the construction of functional graphene assemblies. To improve the performance of graphene-based materials, structurally intact GO should be prepared as a precursor for high-quality graphene; however, solution chemical methods have been constantly challenged by a structural integrity versus fabrication yield trade-off. Here, we report a wet chemical method for the high-efficiency production of a high-quality graphene oxide precursor, with all steps conducted at room-temperature. The functionalization of graphite was performed under temperature and water content control in a concentrated sulfuric acid-potassium permanganate system, and the resulting GO showed a monolayer yield of over 120%. We show that the increased production yield comes from the high functionalization degree and, more interestingly, the functional groups on GO were proven to be removable upon reduction with hydroiodic acid, which produced high-quality graphene-based materials.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA