Second harmonic generation in multilayer graphene induced by direct electric current

Optical second harmonic generation (SHG) is studied from multilayer graphene films in the presence of DC electric current flowing in the sample plane. Graphene layers are manufactured by chemical vapour deposition (CVD) technique and deposited on an oxidised Si(001) substrate. SHG intensity from graphene layer is found to be negligible in the absence of the DC current, while it increases dramatically with the application of the electric current. The current-induced change of the SHG intensity rises linearly with the current amplitude and changes its sign under the reversal of the current direction to the opposite. The observed effect is explained in terms of the interference of second harmonic radiation reflected from the Si surface and that induced by the DC current in multilayer graphene

Generation of stretched pulses and dissipative solitons at 2 µm from an all-fiber mode-locked laser using carbon nanotube saturable absorbers

We demonstrate for the first time, to the best of our knowledge, a thulium-doped, all-fiber, mode-locked laser using a carbon nanotube saturable absorber, operating in the dissipative-soliton regime and the stretched-pulse-soliton regime. The net dispersion of the laser cavity is adjusted by inserting different lengths of normal dispersion fiber, resulting in different mode-locking regimes. These results could serve as a foundation for the optimization of mode-locked fiber-laser cavity design at the 2 µm wavelength region

Plasma-bioresource-derived multifunctional porous NGQD/AuNP nanocomposites for water monitoring and purification

Multifunctional metal–organic composites with controlled structures and properties are attractive for smart optoelectronic, drug delivery, cancer therapy, clean energy, and environmental applications. Here we develop lightweight, porous metal-graphene composites with uniformly dispersed nitrogen-doped graphene quantum dots (NGQDs) and gold nanoparticles (AuNPs) using reactive non-thermal microplasmas under ambient conditions. Synergy of NGQDs and AuNPs accelerates the polymer cross-linking during synthesis and ensures the requisite properties for simultaneous water monitoring and purification including reliable photoluminescence for heavy metal detection, as well as high adsorption capacity and fast catalytic degradation of organic pollutants. Large-area hierarchical composites with tunable porosity and self-healing ability can be fabricated by the fast and scalable plasma process avoiding toxic chemicals and high temperatures. The composite achieves 120 g g−1 water purification within 60 min at 0.13 mM 4-nitrophenol concentration and is able to monitor the water quality against Hg2+ with the detection limit of 2.2 μM, producing 2880 L kg−1 freshwater per day. Besides, almost 100 % of recalcitrant dye, remazol brilliant blue R, with the concentration of 20 ppm can be adsorbed by the composite in 120 min. Our work provides new insights into design and production of high-performance graphene-metal composites for emerging applications.</p

Printing of Crumpled CVD Graphene via Blister-Based Laser-Induced Forward Transfer

The patterning and transfer of a two-dimensional graphene film without damaging its original structure is an urgent and difficult task. For this purpose, we propose the use of the blister-based laser-induced forward transfer (BB-LIFT), which has proven itself in the transfer of such delicate materials. The ease of implementation of laser techniques reduces the number of intermediate manipulations with a graphene film, increasing its safety. The work demonstrates the promise of BB-LIFT of single-layer graphene from a metal surface to a SiO2/Si substrate. The effect of the parameters of this method on the structure of transferred graphene islands is investigated. The relevance of reducing the distance between irradiating and receiving substrates for the transfer of free-lying graphene is demonstrated. The reasons for the damage to the integrity of the carbon film observed in the experiments are discussed. The preservation of the original crystal structure of transferred graphene is confirmed by Raman spectroscopy

Helicity-Sensitive Plasmonic Terahertz Interferometer

Plasmonic interferometry is a rapidly growing area of research with a huge potential for applications in the terahertz frequency range. In this Letter, we explore a plasmonic interferometer based on graphene field effect transistor connected to specially designed antennas. As a key result, we observe helicity- and phase-sensitive conversion of circularly polarized radiation into dc photovoltage caused by the plasmon-interference mechanism: two plasma waves, excited at the source and drain part of the transistor, interfere inside the channel. The helicity-sensitive phase shift between these waves is achieved by using an asymmetric antenna configuration. The dc signal changes sign with inversion of the helicity. A suggested plasmonic interferometer is capable of measuring the phase difference between two arbitrary phase-shifted optical signals. The observed effect opens a wide avenue for phase-sensitive probing of plasma wave excitations in two-dimensional materials

A robust CoxMg1-xO catalyst for predominantly growing (6,5) single-walled carbon nanotubes

Chirality-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) is one of the most challenging tasks in carbon nanotube synthesis field. During CVD growth, the catalyst plays crucial roles in governing SWCNT nucleation thermodynamics as well as growth kinetics. However, the performances of catalyst are generally sensitive to the metal loading amount in the catalyst and the reaction conditions, like the partial pressure of carbon source and the reaction time. In this work, we have systematically investigated a robust CoxMg1-xO solid solution, which can predominantly yield (6, 5) SWCNTs in a wide range of Co concentration, with a diversity of CO concentrations or a broad-ranging reaction time. Besides, the effect of reaction temperature on SWCNT chirality distribution is demonstrated, the mechanism of which is clarified with the assistance of environmental transmission electron microscopy. Finally, the chirality distribution of SWCNTs grown using CH4 as the carbon source is presented. The effects of carbon sources are discussed in view of SWCNT growth mode. (C) 2019 Elsevier Ltd. All rights reserved