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Mesoporous carbon (m-C) has potential applications as porous electrodes for electrochemical energy storage, but its applications have been severely limited by the inherent fragility and low electrical conductivity. A rational strategy is presented to construct m-C into hierarchical porous structures with high flexibility by using a carbon nanotube (CNT) sponge as a three-dimensional template, and grafting Pt nanoparticles at the m-C surface. This method involves several controllable steps including solution deposition of a mesoporous silica (m-SiO2 ) layer onto CNTs, chemical vapor deposition of acetylene, and etching of m-SiO2 , resulting in a CNT@m-C core-shell or a CNT@m-C@Pt core-shell hybrid structure after Pt adsorption. The underlying CNT network provides a robust yet flexible support and a high electrical conductivity, whereas the m-C provides large surface area, and the Pt nanoparticles improves interfacial electron and ion diffusion. Consequently, specific capacitances of 203 and 311â F g(-1) have been achieved in these CNT@m-C and CNT@m-C@Pt sponges as supercapacitor electrodes, respectively, which can retain 96 % of original capacitance under large degree compression.
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Carbon nanotube-Si and graphene-Si solar cells have attracted much interest recently owing to their potential in simplifying manufacturing process and lowering cost compared to Si cells. Until now, the power conversion efficiency of graphene-Si cells remains under 10% and well below that of the nanotube-Si counterpart. Here, we involved a colloidal antireflection coating onto a monolayer graphene-Si solar cell and enhanced the cell efficiency to 14.5% under standard illumination (air mass 1.5, 100 mW/cm(2)) with a stable antireflection effect over long time. The antireflection treatment was realized by a simple spin-coating process, which significantly increased the short-circuit current density and the incident photon-to-electron conversion efficiency to about 90% across the visible range. Our results demonstrate a great promise in developing high-efficiency graphene-Si solar cells in parallel to the more extensively studied carbon nanotube-Si structures.
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Suministros de Energía Eléctrica , Grafito/química , Silicio/química , Coloides/química , Nanotubos de Carbono/química , Energía SolarRESUMEN
Modifying conventional materials with new recipes represents a straightforward yet efficient way to realize large-scale applications of new materials. Electrochemically reduced graphene oxide (ERGO) coated carbon fibres (CFs), prepared as fibre-like supercapacitor electrodes, exhibited excellent electrochemical energy storage performance. Upon addition of only a small amount (~1 wt%) of ERGO, the hybrid fibres showed superior electrochemical capacitances (nearly three orders of magnitude enhanced) compared to pure CFs in both aqueous and gel electrolytes. Meanwhile, the energy density did not decrease notably as the power density increased. The superior capacitive performance could be attributed to the synergistic effect between wrinkled and porous ERGO sheets and highly conductive CFs. This fibre electrode material also offered advantages such as easy operation, mass production capability, mechanical flexibility and robustness, and could have an impact on a wide variety of potential applications in energy and electronic fields.
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Flexible all-solid-state supercapacitors based on graphene fibers are demonstrated in this study. Surface-deposited oxide nanoparticles are used as pseudo-capacitor electrodes to achieve high capacitance. This supercapacitor electrode has an areal capacitance of 42 mF cm(-2), which is comparable to the capacitance for fiber-based supercapacitors reported to date. During the bending and cycling of the fiber-based supercapacitor, the stability could be maintained without sacrificing the electrochemical performance, which provides a novel and simple way to develop flexible, lightweight and efficient graphene-based devices.
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Previous fiber-shaped solar cells are based on polymeric materials or dye-sensitized wide band-gap oxides. Here, we show that efficient fiber solar cells can be made from semiconducting nanostructures (e.g. CdSe) with smaller band-gap as the light absorption material. We directly grow a vertical array of CdSe nanowires uniformly around a core metal wire and make the device by covering the top of nanowires with a carbon nanotube (CNT) film as the porous transparent electrode. The CdSe-CNT fiber solar cells show power conversion efficiencies of 1-2% under AM 1.5 illumination after the nanowires are infiltrated with redox electrolyte. We do not use a secondary metal wire (e.g. Pt) as in conventional fiber-shaped devices, instead, the end part of the CNT film is condensed into a conductive yarn to serve as the secondary electrode. In addition, our CdSe nanowire-based photoelectrochemical fiber solar cells maintain good flexibility and stable performance upon rotation and bending to large angles.
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Compuestos de Cadmio/química , Suministros de Energía Eléctrica , Nanocables/química , Compuestos de Selenio/química , Electroquímica , Electrodos , Nanotubos de Carbono/química , Tamaño de la Partícula , Procesos Fotoquímicos , Porosidad , Propiedades de SuperficieRESUMEN
Deposition of nanostructures such as carbon nanotubes on Si wafers to make heterojunction structures is a promising route toward high efficiency solar cells with reduced cost. Here, we show a significant enhancement in the cell characteristics and power conversion efficiency by growing a silicon oxide layer at the interface between the nanotube film and Si substrate. The cell efficiency increases steadily from 0.5% without interfacial oxide to 8.8% with an optimal oxide thickness of about 1 nm. This systematic study reveals that formation of an oxide layer switches charge transport from thermionic emission to a mixture of thermionic emission and tunneling and improves overall diode properties, which are critical factors for tailoring the cell behavior. By controlled formation and removal of interfacial oxide, we demonstrate oscillation of the cell parameters between two extreme states, where the cell efficiency can be reversibly altered by a factor of 500. Our results suggest that the oxide layer plays an important role in Si-based photovoltaics, and it might be utilized to tune the cell performance in various nanostructure-Si heterojunction structures.
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The thermo-oxidative behavior crucial to the applicability of ethylcellulose (EC) oleogels is characterized. Not only did we take into account the composition of the gel network in relation to textural attributes, but also the dynamic chemical changes occurred during formation, heating, and holding of the gels. EC oleogel oxidative stability showed that at 6.0% EC100 concentration in the oleogels the movement of liquid oil trapped in the gel network was hindered by its high viscosity and stable gel network, thus retarding oxidation. Processing temperatureâ¯≤â¯120⯰C for <2â¯h was recommended when incorporated in food systems to minimize oxidation. As for the measurement of oxidative stability in general, p-AnV was found suitable in depicting oxidation of EC oleogels. Meanwhile, both Rao and Rad acquired from 1H NMR spectra could serve as reliable oxidative indicators to gauge total oxidation of EC oleogels during storage.
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Celulosa/análogos & derivados , Celulosa/química , Espectroscopía de Resonancia Magnética , Compuestos Orgánicos/química , Oxidación-Reducción , Reología , Temperatura de Transición , ViscosidadRESUMEN
A novel shortening was developed based on oleogels structured by ethylcellulose (EC) polymers. The texture and oil retention ability of EC oleogels were characterized against the level of viscosity of different grades of EC, as well as the rheological properties in relation to the polymer structure in the gel network. EC100, which has an average viscosity of 100 cP, was selected as the most suitable organogelator at 4% (w/w) in combination with base oil (30% degree of saturation by mixing palm stearin and soybean oil) to form the shortening. Triglyceryl monostearate (TMS) was found to be the most effective emulsifier as evidenced by its ability to strengthen air-incorporation ability of the shortening while creating evenly distributed fine crystals in the system. The EC100 shortening was able to create breads with excellent specific volume, indicating its ability to incorporate air bubbles during dough development and to serve as an antifirming agent to create bread with stable soft texture. PRACTICAL APPLICATION: In the present study, we attempted to create a novel shortening by employing oleogels structured by ethylcellulose (EC), the most promising gelation agent to develop gel network capable of replacing solid fat without health concerns. EC oleogels in shortening with detailed characterization of the shortening microstructure in relation to its functional properties was elucidated. The optimal formulation in relation to preservation of gel structure and consistency with enhanced moisture and air retention were also identified.
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Celulosa/análogos & derivados , Grasas de la Dieta/análisis , Pan/análisis , Celulosa/química , Culinaria/métodos , Emulsionantes , Geles/química , Glicéridos/química , Compuestos Orgánicos/química , Aceite de Palma/química , Polímeros/química , Reología , Aceite de Soja/química , ViscosidadRESUMEN
OBJECTIVE: To check the expression of leukemia inhibitory factor (Lif) mRNA, and to study the impact of ovarian stimulation on the ability of embryo implantation in mice. METHODS: Pregnancy models of mice were established. The relationship between the implantation of ovarian stimulated embryos and the expression of Lif mRNA in mice metrium was analyzed. RESULTS: The group of recipients which the transfered embryos were from stimulated cycles had lower pregnancy and implantation rate compared with the group of recipients which the transfered embryos were from non-stimulated cycles (20.00%, 8.33% vs 55.00%, 35.00%). The Lif mRNA expression was similar in the groups of recipients which the transfered embryos were from stimulated and non-stimulated cycles, so was in the groups of recipients which had single or more than one baby, but higher in the group of pregnancy recipients than in the group of unpregnancy recipients. CONCLUSION: Ovarian stimulation may reduce the ability of embryo implantation in mice. Lif mRNA expression is related to the implantation, but not parallel to the number of implantation.
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Implantación del Embrión , Endometrio/metabolismo , Factor Inhibidor de Leucemia/genética , Inducción de la Ovulación , Animales , Femenino , Regulación del Desarrollo de la Expresión Génica , Masculino , Ratones , Embarazo , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
This study was aimed to explore a simple and applicable method of separating mature sperms from human testicular tissue for intracytoplasmic sperm injection and embryo transfer. The suspension of human testicular tissue was cultured in 10% human serum albumin and human tubule fluid with different concentrations (0 u/ml; 50 u/ml; 100 u/ml; 150 u/ml; 200 u/ml) of hyaluronidase for 24 h, and then the Percoll gradient centrifugation was processed to separate the sperms; meanwhile the sperms were counted and graded according to their motility. The difference in quality and quantity among the groups and the difference between the groups and the zero-hour culturing group were detected. It was shown that the four hyaluronidase-treated groups contained large quantity and high quality of sperms as compared with the two contrast groups (P<0.01). The groups in the solution of 50 u/ml, 100 u/ml and 150 u/ml concentrations of hyaluronidase had almost the same amount of sperms that displayed higher motility as compared against the sperms in the group treated with 200 u/ml concentration of hyaluronidase (P<0.01). There was no difference between the two contrast groups (P>0.05), or among the groups treated with 50 u/ml, 100 u/ml, and 150 u/ml of hyaluronidase concentration (P>0.05). This method of adopting hyaluronidase with Percoll gradient centrifugation in the process for separating mature sperms from human testicular tissue is applicable. It can increase the quantity and quality of sperms separated from testicular tissue suspensions when adequate concentrations of hyaluronidase is used.
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Separación Celular/métodos , Espermatozoides/citología , Testículo/citología , Adulto , Células Cultivadas , Relación Dosis-Respuesta a Droga , Humanos , Hialuronoglucosaminidasa/farmacología , MasculinoRESUMEN
Applications of mesoporous silica (m-SiO2) have suffered from its fragility (monolithic m-SiO2 easily collapses under compression) and limited internal molecular exchange through small channels. Previously reported hierarchical porous m-SiO2 structures containing interconnected macropores could improve adsorption properties, but they were still intrinsically fragile without sufficient mechanical strength to sustain deformation. Here, we embed a three-dimensional carbon nanotube (CNT) skeleton into m-SiO2 to fabricate bulk, robust sponges that can be compressed to large strains (60% volume reduction) repeatedly in both air and water. This is done by directly casting a uniform m-SiO2 layer with tunable thickness onto the surface of CNTs while maintaining the original network and open porous structure, resulting in a core-shell CNT@m-SiO2 hybrid sponge. By pumping fluid through the CNT@m-SiO2 sponges under cyclic compression, the adsorption rate and efficiency of dye molecules can be significantly enhanced due to the mesoporous coating on CNTs and enhanced fluid exchange throughout internal pores. The CNT@m-SiO2 sponges may be used as robust and flexible adsorption media, and chemical and biological sensors with high performance.
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Nanotubos de Carbono/química , Dióxido de Silicio/química , Adsorción , Colorantes/química , Difusión , Tamaño de la Partícula , Porosidad , Rodaminas/químicaRESUMEN
Design and fabrication of structurally optimized electrode materials are important for many energy applications such as supercapacitors and batteries. Here, we report a three-component, hierarchical, bulk electrode with tailored microstructure and electrochemical properties. Our supercapacitor electrode consists of a three-dimensional carbon nanotube (CNT) network (also called sponge) as a flexible and conductive skeleton, an intermediate polymer layer (polypyrrole, PPy) with good interface, and a metal oxide layer outside providing more surface area. These three components form a well-defined core-double-shell configuration that is distinct from simple core-shell or hybrid structures, and the synergistic effect leads to enhanced supercapacitor performance including high specific capacitance (even under severe compression) and excellent cycling stability. The mechanism study reveals that the shell sequence is a key factor; in our system, the CNT-PPy-MnO2 structure shows higher capacitance than the CNT-MnO2-PPy sequence. Our porous core-double-shell sponges can serve as freestanding, compressible electrodes for various energy devices.
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Graphene nanoribbon aerogels are fabricated by directly unzipping multi-walled carbon nanotube sponges. These fascinating materials have potential applications as high performance nanocomposites and supercapacitor electrodes.
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Introducing stretchability and elasticity into carbon nanotube (CNT) yarns could extend their applications to areas such as stretchable and deformable fiber-based devices and strain sensors. Here, we convert a straight and inelastic yarn into a highly elastic structure by spinning a predefined number of helical loops along the yarn, resulting in a short helical segment with smooth structural transition to the straight portions. The loop-forming process is well controlled, and the obtained straight-helical-straight hybrid yarn is freestanding, stable, and based entirely on CNTs. The elastic and conductive yarns can be stretched to moderate tensile strains (up to 25%) repeatedly for 1000 cycles without producing residual deformation, with a simultaneous and linear change of electrical resistance depending on the strain. Our results indicate that conventional straight CNT yarns could be used as fiber-shaped strain sensors by simple structural modification.
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Introducing twists into carbon nanotube yarns could produce hierarchical architectures and extend their application areas. Here, we utilized such twists to produce elastic strain sensors over large strain (up to 500%) and rotation actuators with high energy density. We show that a helical nanotube yarn can be overtwisted into highly entangled, macroscopically random but locally organized structures, consisting of mostly double-helix segments intertwined together. Pulling the yarn ends completely resolved the entanglement in an elastic and reversible way, yielding large tensile strains with linear change in electrical resistance. Resolving an entangled yarn and releasing its twists could simultaneously rotate a heavy object (30 000 times the yarn weight) for more than 1000 cycles at high speed. The rotational actuation generated from a single entangled yarn produced energy densities up to 8.3 kJ/kg, and maintained similar capacity during repeated use. Our entangled CNT yarns represent a complex self-assembled system with applications as large-range strain sensors and robust rotational actuators.
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Técnicas Biosensibles/instrumentación , Nanofibras/química , Nanofibras/ultraestructura , Nanotecnología/instrumentación , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestructura , Transductores , Módulo de Elasticidad , Transferencia de Energía , Diseño de Equipo , Análisis de Falla de Equipo , Ensayo de Materiales , Conformación Molecular , Rotación , TorqueRESUMEN
Developing flexible and deformable supercapacitor electrodes based on porous materials is of high interest in energy related fields. Here, we show that carbon nanotube sponges, consisting of highly porous conductive networks, can serve as compressible and deformation-tolerant supercapacitor electrodes in aqueous or organic electrolytes. In aqueous electrolytes, the sponges maintain a similar specific capacitance (>90% of the original value) under a predefined compressive strain of 50% (corresponding to a volume reduction of 50%), and retain more than 70% of the original capacitance under 80% strain while the volume normalized capacitance increases by 3-fold. The sponge electrode maintains a stable performance after 1000 large strain compression cycles. A coin-shaped cell assembled with these sponges shows excellent stability over 15,000 charging cycles with negligible degradation after 500 cycles. Our results indicate that carbon nanotube sponges have the potential to fabricate deformable supercapacitor electrodes with stable performance.
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Tailoring the structure and properties of graphene fibers is an important step toward practical applications. Here, we report macroscopic, long graphene ribbons formed by combining electrostatic interaction and shear stress during the wet-spinning process. The graphene ribbons are flexible and can be woven into complex structures, and the ribbon morphology can be tailored by controlling the orientation of wrinkles to obtain elasticity within a modest strain. We demonstrate several potential applications of pure or Pt-graphene hybrid ribbons as elastic strain sensors, counter electrodes for dye-sensitized fiber solar cells with cell efficiencies reaching 4.69% under standard illumination and 6.41% with a back reflector, and woven fabric supercapacitor electrodes. Our method can directly fabricate meter-long graphene ribbons with controlled structure and high performance as both energy conversion and energy storage materials.
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The strength and flexibility of carbon nanotubes (CNTs) allow them to be constructed into a variety of innovated architectures with fascinating properties. Here, we show that CNTs can be made into a highly twisted yarn-derived double-helix structure by a conventional twist-spinning process. The double-helix is a stable and hierarchical configuration consisting of two single-helical yarn segments, with controlled pitch and unique mechanical properties. While one of the yarn components breaks early under tension due to the highly twisted state, the second yarn produces much larger tensile strain and significantly prolongs the process until ultimate fracture. In addition, these elastic and conductive double-helix yarns show simultaneous and reversible resistance change in response to a wide range of input sources (mechanical, photo, and thermal) such as applied strains or stresses, light illumination, and environmental temperature. Our results indicate that it is possible to create higher-level, more complex architectures from CNT yarns and fabricate multifunctional nanomaterials with potential applications in many areas.
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We present the photovoltaic properties of heterojunctions made from single-walled carbon nanotube (SWNT) fibers and n-type silicon wafers. The use of the opaque SWNT fiber allows photo-generated holes to transport along the axis direction of the fiber. The heterojunction solar cells show conversion efficiencies of up to 3.1% (actual) and 10.6% (nominal) at AM1.5 condition. In addition, the use of strong, environmentally benign carbon nanotube fibers provides excellent structural stability of the photovoltaic devices.