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Carbon Nanodots as Feedstock for a Uniform Hematite‐Graphene Nanocomposite

2018-11-13T10:35:08+00:00November 13th, 2018|Categories: Publications|Tags: |

Finely dispersed hematite nanoparticles in a carbon nanodot‐derived 3D‐graphene matrix show enhanced electrochemical performance in electrochemical double layer capacitors. Abstract High degrees of dispersion are a prerequisite for functional composite materials for applications in electronics such as sensors, charge and data storage, and catalysis. The use of small precursor materials can be a decisive factor in achieving a high degree of dispersion. In this study, carbon nanodots are used to fabricate a homogeneous, finely dispersed Fe2O3‐graphene composite aerogel in a one‐step conversion process from a precursor mixture. The laser‐assisted conversion of small size carbon nanodots enables a uniform distribution of 6.5 nm Fe2O3 nanoparticles during the formation of a highly conductive carbon matrix. Structural and electrochemical characterization shows that the features of both material entities are maintained and successfully integrated. The presence of Fe2O3 nanoparticles has a positive effect on the active surface area of the carbon aerogel and thus on the capacitance of the material. This is demonstrated by testing the performance of the composite in supercapacitors. Faradaic reactions are exploited in an aqueous electrolyte through the high accessible surface of the incorporated small Fe2O3 nanoparticles boosting the specific capacitance of the 3D turbostratic graphene network significantly.

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3D 3C‐SiC/Graphene Hybrid Nanolaminate Films for High‐Performance Supercapacitors

2018-11-11T14:34:28+00:00November 11th, 2018|Categories: Publications|Tags: , |

High‐performance electrical double layer capacitors and pseudocapacitors are fabricated and compared using vertically aligned 3C‐SiC/graphene nanolaminate films in both aqueous and organic solutions. Their big and stable capacitances and high power and energy densities result from a 3D alternating structure of 3C‐SiC and graphene layers inside these chemical vapor deposited films, their high surface areas, and excellent conductivity. Abstract High‐performance supercapacitors feature big and stable capacitances and high power and energy densities. To fabricate high‐performance supercapacitors, 3D 3C‐SiC/graphene hybrid nanolaminate films are grown via a microwave plasma‐assisted chemical vapor deposition technique. Such films consist of 3D alternating structures of vertically aligned 3C‐SiC and graphene layers, leading to high surface areas and excellent conductivity. They are further applied as the capacitor electrodes to construct electrical double layer capacitors (EDLCs) and pseudocapacitors (PCs) in both aqueous and organic solutions. The capacitance for an EDLC in aqueous solutions is up to 549.9 µF cm−2, more than 100 times higher than that of an epitaxial 3C‐SiC film. In organic solutions, it is 297.3 µF cm−2. The pseudocapacitance in redox‐active species (0.05 Fe(CN)63−/4−) contained aqueous solutions is as high as 62.2 mF cm−2. The capacitance remains at 98% of the initial value after 2500 charging/discharging cycles, indicating excellent cyclic stability. In redox‐active species (0.01 m ferrocene) contained organic solutions, it is 16.6 mF cm−2. Energy and power densities of a PC in aqueous solution are 11.6 W h kg−1 and 5.1 kW kg−1, respectively. These vertically aligned 3C‐SiC/graphene hybrid nanolaminate films are thus promising

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Microstructural Degradation of Ni‐Rich Li[NixCoyMn1−x−y]O2 Cathodes During Accelerated Calendar Aging

2018-11-11T14:34:26+00:00November 11th, 2018|Categories: Publications|Tags: |

Microstructural degradation of Ni‐rich Li[Nix Coy Mn1–x–y]O2 cathode materials during calendar aging is reported. Because of parasitic reactions, microcracks develop and remain across the entire secondary particle, even after discharging. An NiO‐like phase rock‐salt structure accumulates and exfoliates from the main particles, continuously exposing fresh surfaces. This phenomenon reflects in the electrochemical performance including the discharge capacity and the voltage profile. Abstract Because electric vehicles (EVs) are used intermittently with long resting periods in the fully charged state before driving, calendar aging behavior is an important criterion for the application of Li‐ion batteries used in EVs. In this work, Ni‐rich Li[Ni xCo yMn1 −x−y]O2 (x = 0.8 and 0.9) cathode materials with high energy densities, but low cycling stabilities are investigated to characterize their microstructural degradation during accelerated calendar aging. Although the particles seem to maintain their crystal structures and morphologies, the microcracks which develop during calendar aging remain even in the fully discharged state. An NiO‐like phase rock‐salt structure of tens of nanometers in thickness accumulates on the surfaces of the primary particles through parasitic reactions with the electrolyte. In addition, the passive layer of this rock‐salt structure near the microcracks is gradually exfoliated from the primary particles, exposing fresh surfaces containing Ni4+ to the electrolyte. Interestingly, the interior primary particles near the microcracks have deteriorated more severely than the outer particles. The microstructural degradation is worsened with increasing Ni contents in the cathode materials, directly affecting electrochemical performances such as the reversible capacities and voltage profiles.

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Functionalized MoS2 Nanovehicle with Near‐Infrared Laser‐Mediated Nitric Oxide Release and Photothermal Activities for Advanced Bacteria‐Infected Wound Therapy

2018-11-11T14:34:25+00:00November 11th, 2018|Categories: Publications|Tags: |

A novel 808 nm laser‐mediated nitric oxide (NO)‐releasing nanovehicle (MoS2‐BNN6) based on simple assembly of α‐ cyclodextrin‐modified MoS2 nanosheets with a heat‐sensitive NO donor (BNN6) is developed. The nanovehicle possesses a synergetic photothermal therapy/NO antibacterial function for low‐cost, rapid, and effective action against typical Gram’s bacteria as well as promotion of wound healing. Abstract The rising dangers of bacterial infections have created an urgent need for the development of a new generation of antibacterial nanoagents and therapeutics. A new near‐infrared 808 nm laser‐mediated nitric oxide (NO)‐releasing nanovehicle (MoS2‐BNN6) is reported through the simple assembly of α‐cyclodextrin‐modified MoS2 nanosheets with a heat‐sensitive NO donor N,N′‐di‐sec‐butyl‐N,N′‐dinitroso‐1,4‐phenylenediamine (BNN6) for the rapid and effective treatment of three typical Gram‐negative and Gram‐positive bacteria (ampicillin‐resistant Escherichia coli, heat‐resistant Escherichia faecalis, and pathogen Staphylococcus aureus). This MoS2‐BNN6 nanovehicle has good biocompatibility and can be captured by bacteria to increase opportunities of NO diffusion to the bacterial surface. Once stimulated by 808 nm laser irradiation, the MoS2‐BNN6 nanovehicle not only exhibits photothermal therapy (PTT) efficacy but also can precisely control NO release, generating oxidative/nitrosative stress. The temperature‐enhanced catalytic function of MoS2 induced by 808 nm laser irradiation simultaneously accelerates the oxidation of glutathione. This acceleration disrupts the balance of antioxidants, ultimately resulting in significant DNA damage to the bacteria. Within 10 min, the MoS2‐BNN6 with enhanced PTT/NO synergetic antibacterial function achieves >97.2% inactivation of bacteria. The safe synergetic therapy strategy can also effectively repair wounds through the formation of collagen fibers and elimination of inflammation during tissue

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Recent Progress of Janus 2D Transition Metal Chalcogenides: From Theory to Experiments

2018-11-11T14:34:23+00:00November 11th, 2018|Categories: Publications|Tags: |

Janus 2D transition metal chalcogenides have gained considerable attention for various applications due to the structural asymmetry and distinct properties. This review presents an overview of current theoretical and experimental progress in the development of Janus 2D transition metal chalcogenides. The challenges and future prospects for the further development of Janus 2D materials are also discussed. Abstract Since the discovery of graphene, 2D materials with various properties have gained increasing attention in fields such as novel electronic, optic, spintronic, and valleytronic devices. As an important derivative of 2D materials, Janus 2D materials, such as Janus transition metal chalcogenides (TMDs), have become a research hot spot in recent years. Janus 2D materials with mirror asymmetry display novel properties, such as the Rashba effect and normal piezoelectric polarization, providing great promise for their application in sensors, actuators, and other electromechanical devices. Here, the current theoretical and experimental progresses made in the development of Janus 2D TMDs, including their structure and stability, electronic properties, fabrication, and the results of their characterization are reported. Finally, the future prospects for the further development of Janus 2D materials are considered.

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Photoresponsive Devices: Ultrahigh Photoresponsive Device Based on ReS2/Graphene Heterostructure (Small 45/2018)

2018-11-11T14:34:21+00:00November 11th, 2018|Categories: Publications|Tags: , , |

In article number 1802593, Changgu Lee and co‐workers develop a photodetector based on a ReS2/graphene heterostructure, which exhibits outstanding photoresponsivity, detectivity, and ultrafast responsivity due to the excellent light absorption property of ReS2 and high carrier mobility of graphene. The interface between ReS2 and graphene facilitates a high photocurrent because of the photogating effect under the applied gate voltage.

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Microstructural Degradation of Ni‐Rich Li[NixCoyMn1−x−y]O2 Cathodes During Accelerated Calendar Aging

2018-11-10T00:36:43+00:00November 9th, 2018|Categories: Publications|Tags: |

Microstructural degradation of Ni‐rich Li[Nix Coy Mn1–x–y]O2 cathode materials during calendar aging is reported. Because of parasitic reactions, microcracks develop and remain across the entire secondary particle, even after discharging. An NiO‐like phase rock‐salt structure accumulates and exfoliates from the main particles, continuously exposing fresh surfaces. This phenomenon reflects in the electrochemical performance including the discharge capacity and the voltage profile. Abstract Because electric vehicles (EVs) are used intermittently with long resting periods in the fully charged state before driving, calendar aging behavior is an important criterion for the application of Li‐ion batteries used in EVs. In this work, Ni‐rich Li[Ni xCo yMn1 −x−y]O2 (x = 0.8 and 0.9) cathode materials with high energy densities, but low cycling stabilities are investigated to characterize their microstructural degradation during accelerated calendar aging. Although the particles seem to maintain their crystal structures and morphologies, the microcracks which develop during calendar aging remain even in the fully discharged state. An NiO‐like phase rock‐salt structure of tens of nanometers in thickness accumulates on the surfaces of the primary particles through parasitic reactions with the electrolyte. In addition, the passive layer of this rock‐salt structure near the microcracks is gradually exfoliated from the primary particles, exposing fresh surfaces containing Ni4+ to the electrolyte. Interestingly, the interior primary particles near the microcracks have deteriorated more severely than the outer particles. The microstructural degradation is worsened with increasing Ni contents in the cathode materials, directly affecting electrochemical performances such as the reversible capacities and voltage profiles.

Published in: "Small".

Recent Progress of Janus 2D Transition Metal Chalcogenides: From Theory to Experiments

2018-11-10T00:36:41+00:00November 9th, 2018|Categories: Publications|Tags: |

Janus 2D transition metal chalcogenides have gained considerable attention for various applications due to the structural asymmetry and distinct properties. This review presents an overview of current theoretical and experimental progress in the development of Janus 2D transition metal chalcogenides. The challenges and future prospects for the further development of Janus 2D materials are also discussed. Abstract Since the discovery of graphene, 2D materials with various properties have gained increasing attention in fields such as novel electronic, optic, spintronic, and valleytronic devices. As an important derivative of 2D materials, Janus 2D materials, such as Janus transition metal chalcogenides (TMDs), have become a research hot spot in recent years. Janus 2D materials with mirror asymmetry display novel properties, such as the Rashba effect and normal piezoelectric polarization, providing great promise for their application in sensors, actuators, and other electromechanical devices. Here, the current theoretical and experimental progresses made in the development of Janus 2D TMDs, including their structure and stability, electronic properties, fabrication, and the results of their characterization are reported. Finally, the future prospects for the further development of Janus 2D materials are considered.

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Photoresponsive Devices: Ultrahigh Photoresponsive Device Based on ReS2/Graphene Heterostructure (Small 45/2018)

2018-11-10T00:36:38+00:00November 9th, 2018|Categories: Publications|Tags: , , |

In article number 1802593, Changgu Lee and co‐workers develop a photodetector based on a ReS2/graphene heterostructure, which exhibits outstanding photoresponsivity, detectivity, and ultrafast responsivity due to the excellent light absorption property of ReS2 and high carrier mobility of graphene. The interface between ReS2 and graphene facilitates a high photocurrent because of the photogating effect under the applied gate voltage.

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Glass‐Fabric Reinforced Ag Nanowire/Siloxane Composite Heater Substrate: Sub‐10 nm [email protected] Oxide Nanosheet for Sensitive Flexible Sensing Platform

2018-11-07T08:35:38+00:00November 7th, 2018|Categories: Publications|Tags: , |

A highly sensitive flexible sensing platform is successfully achieved by integrating ultrathin Pt‐loaded SnO2 nanosheets and Ag nanowires embedded flexible hybrimer heater. As a result, via tailored combination of Pt‐SnO2 NSs with AgNW‐GFRVPH film substrate, not only improved bendability with high thermal stability but also extremely sensitive and selective DMS sensing properties are obtained. Abstract The development of flexible chemiresistors is imperative for real‐time monitoring of air quality and/or human physical conditions without space constraints. However, critical challenges such as poor sensing characteristics, vulnerability under toxic chemicals, and weak reliability hinder their practical use. In this work, for the first time, an ultrasensitive flexible sensing platform is reported by assembling Pt loaded thin‐layered (≈10 nm) SnO2 nanosheets (Pt‐SnO2 NSs) based 2D sensing layers on Ag nanowires embedded glass‐fabric reinforced vinyl–phenyl siloxane hybrid composite substrate (AgNW‐GFRVPH film) as a heater. The thermally stable AgNW‐GFRVPH film based heater is fabricated by free radical polymerization of vinyl groups in vinyl–phenyl oligosiloxane and phenyltris(dimethylvinylsiloxy)silane with Ag NW and glass‐fabric, showing outstanding heat generation (≈200 °C), high dimensional stability (13 ppm °C−1), and good thermal stability (≈350 °C). The Pt‐SnO2 NSs, which are synthesized by calcination of Sn precursor coated graphene oxide (GO) sheets and subsequent Pt functionalization, exhibit high mechanical flexibility and superior response (R air/R gas = 4.84) to 1 ppm level dimethyl sulfide. Taking these advantages, GO‐templated oxide NSs combined with a highly stable AgNW‐GFRVPH film heater exhibits the best dimethyl sulfide sensing performance compared to state‐of‐the‐art flexible chemiresistors, enabling them

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Sphere‐to‐Multipod Transmorphic Change of Nanoconfined Pt Electrocatalyst during Oxygen Reduction Reaction

2018-11-07T08:35:31+00:00November 7th, 2018|Categories: Publications|Tags: , |

Pt nanoconfined within holes of graphene exhibits excellent durability along repeated oxygen reduction. The Ostwald ripening dominant over the surface migration in the nanoconfined situation evolves spherical multifaceted Pt particles to the {110}‐dominant dendritic multipods. Abstract An oxygen reduction reaction (ORR) catalyst/support system is designed to have Pt nanoparticles nanoconfined in a nanodimensionally limited space. Holey crumpled reduced graphene oxide plates (hCR‐rGO) are used as a carbon support for Pt loading. As expected from interparticular Pt‐to‐Pt distance of Pt‐loaded hCR‐rGO longer than that of Pt/C (Pt‐loaded carbon black as a practical Pt catalyst), the durability of ORR electroactivity along cycles is improved by replacing the widely used carbon black with hCR‐rGO. Unexpected morphological changes of Pt are electrochemically induced during repeated ORR processes. Spherical multifaceted Pt particles are evolved to {110}‐dominant dendritic multipods. Nanoconfinement of a limited number of Pt within a nanodimensionally limited space is responsible for the morphological changes. The improved durability observed from Pt‐loaded hCR‐rGO originates from 1) dendritic pod structure of Pt exposing more active sites to reactants and 2) highly ORR‐active Pt {110} planes dominant on the surface.

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Epitaxial Synthesis of Blue Phosphorene

2018-11-07T08:35:28+00:00November 7th, 2018|Categories: Publications|Tags: |

Phosphorene is a 2D material with an intrinsic tunable bandgap and high carrier mobility. Epitaxial growth of single‐layer phosphorene on Au(111) is achieved using molecular beam epitaxy. Scanning tunneling microscope images show high‐quality and ordered monolayer phosphorene. Density functional theory calculations support a blue phosphorene layer presenting two different structures. Photoemission (ARPES) measurements reveal a bandgap of at least 0.8 eV. Abstract Phosphorene is a new 2D material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct bandgap and high carrier mobility values, which make it suitable for a large variety of optical and electronic devices. However, the synthesis of single‐layer phosphorene is a major challenge. The standard procedure to obtain phosphorene is by exfoliation. More recently, the epitaxial growth of single‐layer phosphorene on Au(111) was investigated by molecular beam epitaxy and the obtained structure described as a blue phosphorene sheet. In the present study, large areas of high‐quality monolayer phosphorene, with a bandgap value equal to at least 0.8 eV, are synthesized on Au(111). The experimental investigations, coupled with density functional theory calculations, give evidence of two distinct phases of blue phosphorene on Au(111), instead of one as previously reported, and their atomic structures are determined.

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An Elastic Interfacial Transistor Enabled by Superhydrophobicity

2018-11-07T08:35:25+00:00November 7th, 2018|Categories: Publications|Tags: |

A new force‐sensing concept of interfacial field‐effect transistor (IFET) is proposed. Ultrasensitive stress sensing is enabled by deformation of liquid metal droplets on hydrophobic semiconductor nanowires, with the current density further modulated by a field effect at the semiconductor–graphene interface. This study demonstrates a versatile platform that bridges multiple macroscopic interfacial phenomena with nanoelectronic responses. Abstract Enabling mechanical responsiveness in field‐effect transistors (FETs) offers new technological opportunity beyond the reach of existing platforms. Here a new force‐sensing concept is proposed by controlling the wettability of a semiconductor surface, referring to the interfacial field‐effect transistors (IFETs). An IFET made by superhydrophobic semiconductor nanowires (NWs) sandwiched between a layer of 2D electron gas (2DEG) and a conductive Cassie–Baxter (CB) sessile droplet is designed. Following the hydrostatic deformation of the CB droplet upon mechanical stress, an extremely small elastic modulus of 820 pascals vertical to the substrate plane, or ≈100 times softer than Ecoflex rubbers, enabling an excellent stress detection limit down to <10 pascals and a stress sensitivity of 36 kPa−1 is proposed. The IFET exhibits an on/off current ratio exceeding 3 × 104, as the carrier density profile at the NW/2DEG interface is modulated by a partially penetrated electrostatic field. This study demonstrates a versatile platform that bridges multiple macroscopic interfacial phenomena with nanoelectronic responses.

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Charge Density Waves Driven by Peierls Instability at the Interface of Two‐Dimensional Lateral Heterostructures

2018-11-07T08:35:22+00:00November 7th, 2018|Categories: Publications|Tags: , , , , |

Charge density wave (CDW) formation at the one‐dimensional interface embedded in a lateral two‐dimensional (2D) heterostructure comprising blue and black phosphorene is found. The CDW formation is driven by the Peierls instability and substantially modifies the band alignment of the heterostructure. These findings are applicable to other 2D lateral heterostructures and have important implications for their application. Abstract The origin of charge density wave (CDW) observed in low‐dimensional systems is, for long, a subject of intensive debate in contemporary condensed matter physics. Specifically, a simple and well established model, namely, the Peierls instability is often (but not always) used to clearly explain CDW states in real systems. Here, first‐principles density functional theory calculations are used to show CDW formation at a one‐dimensional interface embedded in a lateral heterostructure comprising blue and black phosphorene, even at room temperature. The CDW formation is fully explained by the Peierls mechanism, including a double‐periodicity lattice distortion energy lowering and a bandgap opening. The lattice distortion also substantially modifies the band alignment of the heterostructure. Comparison with a freestanding P chain shows that the structural distortion is confined to one dimension within the heterostructures, ruling out competing non‐Peierls‐type distortions in two dimensions. In addition, similar Peierls‐type distortions for other lateral heterostructures are shown by using the example of a graphene–hexagonal boron nitride heterostructure, which may stimulate related studies in different 2D systems. These findings not only shed more light on the Peierls mechanism, but also have important implications for devices based on 2D lateral

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2D Crystals in Three Dimensions: Electronic Decoupling of Single‐Layered Platelets in Colloidal Nanoparticles

2018-11-07T08:35:19+00:00November 7th, 2018|Categories: Publications|Tags: , |

Optoelectronic properties of 2D crystals are distinct from their bulk counterparts, and advantageous for applications. Band gaps are larger, and sometimes direct, well‐suited for optoelectronic and photocatalytic applications. However, being atomically thin, low density is a bottleneck for quantitative performance. The proposed intercalation of layered materials with short surfactants yields electronically decoupled layers with similar properties as monolayers, but higher cross‐sections. Abstract 2D crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley‐ and spin‐orbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, the formation of stacks of 2D crystals intercalated with small surfactant molecules is proposed. It is shown, using first principles calculations, that the very short surfactant methyl amine electronically decouples the layers. The indirect–direct band gap transition characteristic for Group 6 transition metal dichalcogenides is demonstrated experimentally by observing the emergence of a strong photoluminescence signal for ethoxide‐intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the 2D crystals with electronic properties typical of monolayers. Variation of the surfactant’s chemical potential allows fine‐tuning of electronic properties and potentially elimination of trap states caused by defects.

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“Non‐Naked” Gold with Glucose Oxidase‐Like Activity: A Nanozyme for Tandem Catalysis

2018-11-07T08:35:15+00:00November 7th, 2018|Categories: Publications|Tags: , |

“Non‐naked” gold nanoparticles (Au NPs) with the glucose oxidase (GOx)‐like activity are synthesized by using protein as protector. “Non‐naked” Au NPs show tandem enzyme‐like characteristics, which simultaneously have dual enzyme‐like activities. Moreover, the covalent modification of Au NPs with graphene oxide cannot affect their GOx‐like activity. Furthermore, a one‐pot enzyme‐free strategy is developed for the fast colorimetric detection of glucose. Abstract It has been widely reported that “naked” gold nanoparticles (Au NPs) without protectors have glucose oxidase (GOx)‐like activity, and the use of protectors can inhibit the GOx‐like activity. Here, “non‐naked” Au NPs with GOx‐like activity are synthesized by using protein as protector. Although “naked” Au NPs have peroxidase‐like activity and GOx‐like activity, the optimal pH ranges of the both activities are obviously different. Fortunately, as‐synthesized “non‐naked” Au NPs show the dual enzyme‐like activities at the same pH. So, “non‐naked” Au NPs can be described as “tandem nanozyme.” As another bonus, the participation of protein protector can stabilize the GOx‐like activity and make Au NPs modifiable. Even though Au NPs are connected with graphene oxide (GO), the GOx‐like activity is still not changed. Further, Au NPs‐GO nanocomposites are applied on the one‐pot nonenzymatic glucose colorimetric detection. The “non‐naked” gold not only broadens the species of tandem nanozymes, but also facilitates the functionalization of nanozymes, which is promising for immunoassay, biosensor, and medical treatment.

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Hierarchical Graphene‐Scaffolded Silicon/Graphite Composites as High Performance Anodes for Lithium‐Ion Batteries

2018-11-07T08:35:09+00:00November 7th, 2018|Categories: Publications|Tags: |

Hierarchical graphene‐scaffolded silicon/graphite composites prepared through a self‐assembly process are studied as anodes for lithium‐ion batteries. In the unique hierarchical structure, the Si/graphite composite are encapsulated tightly in the 3D graphene scaffold. The composite containing 5 wt% of Si exhibits an unprecedented utilization ratio of Si and maintains a highly reversible capacity of 445 mA h g−1 even after 300 cycles. Abstract To better couple with commercial cathodes, such as LiCoO2 and LiFePO4, graphite‐based composites containing a small proportion of silicon are recognized as promising anodes for practical application in lithium‐ion batteries (LIBs). However, the prepared Si/C composite still suffers from either rapid capacity fading or the high cost up to now. Here, the facile preparation of hierarchical graphene‐scaffolded silicon/graphite composite is reported. In this designed 3D structure, Si nanoparticles are homogeneously dispersed on commercial graphites and then uniformly encapsulated in the hierarchical graphene scaffold. This hierarchical structure is also well characterized by the synchrotron X‐ray computed nanotomography technique. When evaluated as anodes for LIBs, the hierarchical composite, with the Si weight ratio of 5 wt%, exhibits a reversible capacity of 559 mA h g−1 at 75 mA g−1, suggesting an unprecedented utilization of Si up to 95%. Even at 372 mA g−1, the composite can still maintain a high capacity retention of 90% after 100 cycles. Coupled with the LiFePO4 cathode, the full cell shows the high capacity of 114 mA h g−1 at 170 mA g−1. The excellent Li‐storage properties can be ascribed to the unique designed

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High‐Performance Wafer‐Scale MoS2 Transistors toward Practical Application

2018-11-07T08:35:08+00:00November 7th, 2018|Categories: Publications|Tags: |

An improved synthesis strategy for wafer‐scale MoS2 continuous films by introducing multilayer MoS2 islands to improve the electrical contact and dielectric deposition is developed. The multilayer islands provide an extra amount of exposed edges to guarantee conformal contact with evaporated metal electrodes, while the bottom continuous 1L‐MoS2 serves as a high‐quality field effect transistor channel. Abstract Atomic thin transition‐metal dichalcogenides (TMDs) are considered as an emerging platform to build next‐generation semiconductor devices. However, to date most devices are still based on exfoliated TMD sheets on a micrometer scale. Here, a novel chemical vapor deposition synthesis strategy by introducing multilayer (ML) MoS2 islands to improve device performance is proposed. A four‐probe method is applied to confirm that the contact resistance decreases by one order of magnitude, which can be attributed to a conformal contact by the extra amount of exposed edges from the ML‐MoS2 islands. Based on such continuous MoS2 films synthesized on a 2 in. insulating substrate, a top‐gated field effect transistor (FET) array is fabricated to explore key metrics such as threshold voltage (V T) and field effect mobility (μFE) for hundreds of MoS2 FETs. The statistical results exhibit a surprisingly low variability of these parameters. An average effective μFE of 70 cm2 V−1 s−1 and subthreshold swing of about 150 mV dec−1 are extracted from these MoS2 FETs, which are comparable to the best top‐gated MoS2 FETs achieved by mechanical exfoliation. The result is a key step toward scaling 2D‐TMDs into functional systems and paves the way

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Mesoporous Reduced Graphene Oxide as a High Capacity Cathode for Aluminum Batteries

2018-11-07T08:35:04+00:00November 7th, 2018|Categories: Publications|Tags: , , |

Tailoring the pore size distribution of carbon‐based cathodes is a decisive factor for the electrochemical performance of aluminum batteries. Here, the mesopores in a reduced graphene oxide powder facilitate the movement of large chloroaluminate ions, effectively minimizing the inactive mass content of the electrode and compensating for an ordinary micropore volume. Abstract Research in the field of aluminum batteries has focused heavily on electrodes made of carbonaceous materials. Still, the capacities reported for these multivalent systems remain stubbornly low. It is believed that a high structural quality of graphitic carbons and/or specific surface areas of >1000 m2 g‐1 are key factors to obtain optimal performance and cycling stability. Here an aluminum chloride battery is presented in which reduced graphene oxide (RGO) powder, dried under supercritical conditions, is used as the active cathode material and niobium foil as the current collector. With a specific surface area of just 364 m2 g‐1, the RGO enables a gravimetric capacity of 171 mAh g‐1 at 100 mA g‐1 and remarkable stability over a wide range of current densities (<15% decrease over 100 cycles in the interval 100–20000 mA g‐1). These properties, up to now achieved only with much larger surface area materials, result from the cathode’s tailored mesoporosity. The 20 nm wide mesopores facilitate the movement of the chloroaluminate ions through the RGO, effectively minimizing the inactive mass content of the electrode. This more than compensates for the ordinary micropore volume of the graphene powder.

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Rationally Designed Monodisperse Gd2O3/Bi2S3 Hybrid Nanodots for Efficient Cancer Theranostics

2018-11-07T08:35:03+00:00November 7th, 2018|Categories: Publications|

Monodisperse Gd2O3/Bi2S3 hybrid nanodots are developed as a multifunctional nanotheranostic agent using an albumin nanoreactor for efficient computed tomography/photoacoustics/magnetic resonance imaging and simultaneous photothermal tumor ablation. Abstract Multifunctional nanotheranostic agents are of particular importance in the field of precise nanomedicine. However, a critical challenge remains in the rational fabrication of monodisperse multicomponent nanoparticles with enhanced multifunctional characteristics for efficient cancer theranostics. Here, a rational and facile synthesis of monodisperse Gd2O3/Bi2S3 hybrid nanodots (Gd/Bi‐NDs) is demonstrated as a multifunctional nanotheranostic agent using a albumin nanoreactor for computed tomography (CT)/photoacoustics (PA)/magnetic resonance (MR) imaging and simultaneous photothermal tumor ablation. Two nanoprecipitation reactions in one albumin nanoreactor are simultaneously conducted to generate ultrasmall Gd/Bi‐NDs with both orthorhombic Bi2S3 and cubic Gd2O3 nanostructures. Their hybrid nanostructure generates distinctly enhanced longitudinal relaxivity in the spatially confined albumin nanocage as compared to monocomponent Gd2O3 nanodots. Moreover, such hybrid nanodots possess multiple desirable characteristics including superior photobleaching resistance, efficient cellular uptake, preferable tumor accumulation, good in vivo clearance, and negligible acute toxicity, thereby leading to complementary PA/CT/MR imaging with spatial and anatomic characteristics, as well as effective photothermal tumor ablation without regrowth. These results represent a promising approach to fabricate monodisperse multicomponent nanotheranostic agents for efficient cancer theranostics.

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