Science Advances

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Synthetic WSe2 monolayers with high photoluminescence quantum yield

2019-01-03T00:36:50+00:00January 2nd, 2019|Categories: Publications|Tags: |

In recent years, there have been tremendous advancements in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers

Published in: "Science Advances".

A single-stranded coordination copolymer affords heterostructure observation and photoluminescence intensification

2019-01-03T00:36:49+00:00January 2nd, 2019|Categories: Publications|Tags: |

Few artificial systems can be exfoliated into, and observed as, single wires with lengths of more than several micrometers, and no previous example features a copolymer structure; this is in contrast with biopolymers such as single-strand DNAs. Here, we create a set of one-dimensional coordination copolymers featuring bis(dipyrrinato)zinc complex motifs

Published in: "Science Advances".

Anomalous interfacial stress generation during sodium intercalation/extraction in MoS2 thin-film anodes

2019-01-03T00:36:45+00:00January 2nd, 2019|Categories: Publications|Tags: |

Although the generation of mechanical stress in the anode material is suggested as a possible reason for electrode degradation and fading of storage capacity in batteries, only limited knowledge of the electrode stress and its evolution is available at present. Here, we show real-time monitoring of the interfacial stress of

Published in: "Science Advances".

Discovering the forbidden Raman modes at the edges of layered materials

2018-12-14T20:36:54+00:00December 14th, 2018|Categories: Publications|Tags: , , , , |

The edges of layered materials have unique properties that substantially differ from the body regions. In this work, we perform a systematic Raman study of the edges of various layered materials (MoS2, WS2, WSe2, PtS2, and black phosphorus). The Raman spectra of the edges feature newly observed forbidden Raman modes,

Published in: "Science Advances".

Graphene catalyzes the reversible formation of a C-C bond between two molecules

2018-12-14T20:36:50+00:00December 14th, 2018|Categories: Publications|Tags: |

Carbon deposits are well-known inhibitors of transition metal catalysts. In contrast to this undesirable behavior, here we show that epitaxial graphene grown on Ru(0001) promotes the reversible formation of a C–C bond between –CH2CN and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). The catalytic role of graphene is multifaceted: First, it allows for an efficient

Published in: "Science Advances".

Multifunctional wafer-scale graphene membranes for fast ultrafiltration and high permeation gas separation

2018-11-24T00:36:28+00:00November 23rd, 2018|Categories: Publications|Tags: |

Reliable and large-scale manufacturing routes for perforated graphene membranes in separation and filtration remain challenging. We introduce two manufacturing pathways for the fabrication of highly porous, perforated graphene membranes with sub–100-nm pores, suitable for ultrafiltration and as a two-dimensional (2D) scaffold for synthesizing ultrathin, gas-selective polymers. The two complementary processes—bottom

Published in: "Science Advances".

Realization of flat band with possible nontrivial topology in electronic Kagome lattice

2018-11-16T22:36:24+00:00November 16th, 2018|Categories: Publications|Tags: |

The energy dispersion of fermions or bosons vanishes in momentum space if destructive quantum interference occurs in a frustrated Kagome lattice with only nearest-neighbor hopping. A discrete flat band (FB) without any dispersion is consequently formed, promising the emergence of fractional quantum Hall states at high temperatures. Here, we report

Published in: "Science Advances".

Extremely flat band in bilayer graphene

2018-11-09T20:36:28+00:00November 9th, 2018|Categories: Publications|Tags: |

We propose a novel mechanism of flat band formation based on the relative biasing of only one sublattice against other sublattices in a honeycomb lattice bilayer. The mechanism allows modification of the band dispersion from parabolic to “Mexican hat”–like through the formation of a flattened band. The mechanism is well

Published in: "Science Advances".

Entanglement signatures of emergent Dirac fermions: Kagome spin liquid and quantum criticality

2018-11-09T20:36:26+00:00November 9th, 2018|Categories: Publications|Tags: |

Quantum spin liquids (QSLs) are exotic phases of matter that host fractionalized excitations. It is difficult for local probes to characterize QSL, whereas quantum entanglement can serve as a powerful diagnostic tool due to its nonlocality. The kagome antiferromagnetic Heisenberg model is one of the most studied and experimentally relevant

Published in: "Science Advances".

Evidence for a quantum spin Hall phase in graphene decorated with Bi2Te3 nanoparticles

2018-11-09T20:36:21+00:00November 9th, 2018|Categories: Publications|Tags: |

Realization of the quantum spin Hall effect in graphene devices has remained an outstanding challenge dating back to the inception of the field of topological insulators. Graphene’s exceptionally weak spin-orbit coupling—stemming from carbon’s low mass—poses the primary obstacle. We experimentally and theoretically study artificially enhanced spin-orbit coupling in graphene via

Published in: "Science Advances".

Dynamic assembly of liquid crystalline graphene oxide gel fibers for ion transport

2018-11-02T18:36:23+00:00November 2nd, 2018|Categories: Publications|Tags: , |

Colloidal dispersions with liquid crystallinity hold great promise for fabricating their superstructures. As an example, when graphene oxide (GO) sheets are assembled in the liquid crystalline state, they can turn into ordered macroscopic forms of GO such as fibers via the wet spinning process. Here, we report that by reinforcing

Published in: "Science Advances".

Mass spectrometry imaging of the in situ drug release from nanocarriers

2018-11-01T02:36:30+00:00November 1st, 2018|Categories: Publications|Tags: , |

It is crucial but of a great challenge to study in vivo and in situ drug release of nanocarriers when developing a nanomaterial-based drug delivery platform. We developed a new label-free laser desorption/ionization mass spectrometry (MS) imaging strategy that enabled visualization and quantification of the in situ drug release in

Published in: "Science Advances".

Quantum interference mediated vertical molecular tunneling transistors

2018-10-12T22:36:38+00:00October 12th, 2018|Categories: Publications|Tags: , , |

Molecular transistors operating in the quantum tunneling regime represent potential electronic building blocks for future integrated circuits. However, due to their complex fabrication processes and poor stability, traditional molecular transistors can only operate stably at cryogenic temperatures. Here, through a combined experimental and theoretical investigation, we demonstrate a new design

Published in: "Science Advances".

Observation of long-range dipole-dipole interactions in hyperbolic metamaterials

2018-10-05T20:36:37+00:00October 5th, 2018|Categories: Publications|Tags: |

Dipole-dipole interactions (Vdd) between closely spaced atoms and molecules are related to real photon and virtual photon exchange between them and decrease in the near field connected with the characteristic Coulombic dipole field law. The control and modification of this marked scaling with distance have become a long-standing theme in

Published in: "Science Advances".

Tailoring emergent spin phenomena in Dirac material heterostructures

2018-09-22T02:36:57+00:00September 22nd, 2018|Categories: Publications|Tags: , |

Dirac materials such as graphene and topological insulators (TIs) are known to have unique electronic and spintronic properties. We combine graphene with TIs in van der Waals heterostructures to demonstrate the emergence of a strong proximity-induced spin-orbit coupling in graphene. By performing spin transport and precession measurements supported by ab

Published in: "Science Advances".

2D titanium carbide (MXene) for wireless communication

2018-09-22T02:36:55+00:00September 22nd, 2018|Categories: Publications|Tags: |

With the development of the Internet of Things (IoT), the demand for thin and wearable electronic devices is growing quickly. The essential part of the IoT is communication between devices, which requires radio-frequency (RF) antennas. Metals are widely used for antennas; however, their bulkiness limits the fabrication of thin, lightweight,

Published in: "Science Advances".

Programmable wettability on photocontrolled graphene film

2018-09-15T00:36:40+00:00September 15th, 2018|Categories: Publications|Tags: |

Surface materials with specific wettability play important roles in a wide variety of areas from science to industry. We present a novel paraffin-infused porous graphene film (PIPGF) with programmable wettability. Because of graphene’s photothermal property, the paraffin in the PIPGF was in transition between liquid and solid in response to

Published in: "Science Advances".

In situ manipulation and switching of dislocations in bilayer graphene

2018-08-11T00:36:40+00:00August 11th, 2018|Categories: Publications|Tags: |

Topological defects in crystalline solids are of fundamental interest in physics and materials science because they can radically alter the properties of virtually any material. Of particular importance are line defects, known as dislocations, which are the main carriers of plasticity and have a tremendous effect on electronic and optical

Published in: "Science Advances".

Coherent perfect absorption of nonlinear matter waves

2018-08-11T00:36:37+00:00August 11th, 2018|Categories: Publications|Tags: |

Coherent perfect absorption is the complete extinction of incoming radiation by a complex potential in a physical system supporting wave propagation. The concept was proven for linear waves in a variety of systems including light interacting with absorbing scatterers, plasmonic metasurfaces, and graphene films, as well as sound waves. We

Published in: "Science Advances".

Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS2-xSex

2018-07-20T18:36:21+00:00July 20th, 2018|Categories: Publications|Tags: , |

The hidden (H) quantum state in 1T-TaS2 has sparked considerable interest in the field of correlated electron systems. Here, we investigate ultrafast switches to stable H charge density wave (H-CDW) states observed in 1T-TaS2–xSex, with x = 0 and 0.5 crystals, upon excitation with a single femtosecond laser pulse. In

Published in: "Science Advances".

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