We demonstrate first room temperature, and ultrabright single photon emission from a color center in two-dimensional multilayer hexagonal boron nitride. Density Functional Theory calculations indicate that vacancy-related centers are a likely source of the emission.

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Quantum emission from hexagonal boron nitride monolayers

Heterocyclic pyrrole molecules are in situ aligned and polymerized in the -absence of an oxidant between layers of the 2D Ti3C2Tx (MXene), resulting in high volumetric and gravimetric capacitances with capacitance retention of 92% after 25,000 cycles at a 100 mV s(-1) scan rate.

Pseudocapacitive Electrodes Produced By Oxidant-Free Polymerization of Pyrrole Between the Layers of 2D Titanium Carbide (MXene)

High-performance electromagnetic interference (EMI) shielding materials with ultraflexibility, outstanding mechanical properties, and superior EMI shielding performances are highly desirable for mo

Ultraflexible and Mechanically Strong Double-Layered Aramid Nanofiber-Ti3C2Tx MXene/Silver Nanowire Nanocomposite Papers for High-Performance Electromagnetic Interference Shielding.

2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically 3 graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface-science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive magnetoconductance). Low resistance samples show characteristics of weak-localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 10^{12} cm^{-2} per graphene sheet. The most highly-ordered sample exhibits Shubnikov - de Haas oscillations which correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic techniques, and we demonstrate modulation of the film conductance using a top-gate electrode. These key elements suggest electronic device applications based on nano-patterned epitaxial graphene (NPEG), with the potential for large-scale integration.

Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics

2D transition metal carbides or nitrides, known as MXenes, are a new family of 2D materials with close to 30 members experimentally synthesized and dozens more theoretically investigated. Because o...

MXene/Polymer Membranes: Synthesis, Properties, and Emerging Applications

Graphdiyne (GDY), a newly emerging 2D carbon allotrope, has been widely explored in various fields owing to its outstanding electronic properties such as the intrinsic bandgap and high carrier mobility. Herein, GDY-based photoelectrochemical-type photodetection is realized by spin-coating ultrathin GDY nanosheets onto flexible poly(ethylene terephthalate) (PET) substrates. The GDY-based photodetectors (PDs) demonstrate excellent photo-responsive behaviors with high photocurrent (Pph , 5.98 µA cm- 2 ), photoresponsivity (Rph , 1086.96 µA W- 1 ), detectivity (7.31 × 1010 Jones), and excellent long-term stability (more than 1 month). More importantly, the PDs maintain an excellent Pph after 1000 cycles of bending (4.45 µA cm- 2 ) and twisting (3.85 µA cm- 2 ), thanks to the great flexibility of the GDY structure that is compatible with the flexible PET substrate. Density functional theory (DFT) calculations are adopted to explore the electronic characteristics of GDY, which provides evidence for the performance enhancement of GDY in alkaline electrolyte. In this way, the GDY-based flexible PDs can enrich the fundamental study of GDY and pave the way for the exploration of GDY heterojunction-based photodetection.

Graphdiyne-Based Flexible Photodetectors with High Responsivity and Detectivity

An All-Optical, Actively Q-Switched Fiber Laser by an Antimonene-Based Optical Modulator

Tellurium (Te) exhibits many intriguing properties including thermoelectricity, photoelectricity, piezoelectricity, and photoconductivity, and is widely used in detectors, sensors, transistors, and energy devices. Herein, ultrathin two-dimensional (2D) Te nanosheets were fabricated using a facile and cost-effective liquid-phase exfoliation method. Mixing the as-prepared 2D Te nanosheets with polyvinylpyrrolidone (PVP) provided a uniform 2D Te/PVP membrane. The 2D Te/PVP membrane exhibited excellent mechanical properties, thermal properties, and stability. The nonlinear optical properties of the membrane were characterized over the spectral range of 800 to 1550 nm using open-aperture Z-scan technology. A large nonlinear absorption coefficient of about 10−1 cm GW−1 over the whole tested wavelength range demonstrated the efficient broadband saturable absorptivity of the 2D Te/PVP membrane. Using the 2D Te/PVP membrane as a saturable absorber (SA), a highly stable femtosecond laser with a pulse duration of 829 fs in the communication band was obtained. This work highlights the promise of 2D Te/PVP membranes in ultrafast photonics and Te as a new 2D material for use in photonic devices such as all-optical modulators, switches, and thresholds.

Jia Guo

Papers

MXene/Polymer Membranes: Synthesis, Properties, and Emerging Applications

Graphdiyne-Based Flexible Photodetectors with High Responsivity and Detectivity

An All-Optical, Actively Q-Switched Fiber Laser by an Antimonene-Based Optical Modulator

Two-dimensional tellurium-polymer membrane for ultrafast photonics.

Graphdiyne-Polymer Nanocomposite as a Broadband and Robust Saturable Absorber for Ultrafast Photonics