Synthesis of two-dimensional lead sheets by spark discharge in liquid nitrogen

Abstract

A simple method to synthesize hexagonal sheets of lead, which belong to the class of twodimensional materials, is presented. These objects can be collected on a substrate located under two lead electrodes between which nanosecond-pulsed spark discharges in liquid nitrogen are ignited. The hexagonal sheets are single crystals produced by gas phase condensation. Once nitrogen is fully evaporated, they are oxidized in the air and turned into PbO2. The oxidation process induces stress that may pleat the uppermost sheets or open cracks in the centre of the structure. The thickness of individual objects varies typically from 4 to 20 nm. If the number of discharges exceeds about 2000, two types of PbO2 sticks start being observed: bundles made of nanosticks (5 μm in length and 50 nm of diameter) and isolated stick (20 μm in length and 500 nm in diameter) in addition to sheets. These new nanostructures are mainly due to the way lead electrodes are eroded by the discharge. At the beginning, the anisotropic erosion driven by the orientation of crystallographic planes of lead crystals produces octahedra and nanosticks, these latter growing longer and longer on electrode surfaces as discharges proceed. After about 2000 discharges, nanosticks are long enough to be easily broken, likely by mechanical stress, and fall onto the underlying substrate.

Microwave Plasma Jet in Water: Characterization and Feasibility to Wastewater Treatment

“…When we take the example of in-liquid plasmas generated by nanosecond discharges, these discharges are generated with or without gaseous bubbles, and usually run in spark mode [16][17][18] (i.e., the plasma channel connects two electrodes) or in streamer mode [4][5][6] (i.e., the plasma channel is connected to one electrode). In the case of a spark mode, the plasma-electrode interaction is relatively strong, which leads to erosion issue [19][20][21] and reduces a lifetime of electrodes. In addition, a contamination of plasma treated liquid due to materials from electrode erosion may cause problems, particularly when the size of the particles is very small, and classical purification methods fail to remove them.…”

Crystal structure, morphology and formation mechanism of a novel polymorph of lead dioxide, γ-PbO2

“…The experimental setup for the synthesis of lead oxide nanosheets is presented in detail in the paper recently published by Hamdan et al (2018). Briefly, by pulsed discharges in liquid nitrogen between two wires made of lead and used as electrodes in a pin-to-pin configuration, hexagonal nanosheets were obtained ( Fig.…”

“…Creating high-voltage discharges in liquid nitrogen is a method developed nearly 15 years ago to produce original nanostructures (Sano et al, 2004;Charinpanitkul et al, 2009;Hamdan et al, 2018) by electrode erosion in non-equilibrium conditions (Hamdan et al, 2013;Belmonte et al, 2014). This process is known to exhibit one of the highest production yields of nano-objects by a physical method.…”

“…This # 2019 International Union of Crystallography method initially produces hexagonal nanosheets. However, the synthesis of lead nanosheets is limited by a specific erosion process that produces lead sticks beyond about 2000 discharges rather than hexagonal nanosheets [see the detailed explanation given by Hamdan et al (2018)]. X-ray diffraction being not relevant, we have used energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), highangle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron diffraction to identify the crystal structure of lead nanosheets obtained by this process, in order to explain the lead dioxide morphology inherited from the hexagonal lead nanosheet particles.…”

Synergistic Effect of Plasma and Laser Processes in Liquid for Alloyed-Nanoparticle Synthesis

“…They present the main advantage of being inexpensive, safe and easy to run. They have been successfully used to synthesize core-shell NPs [22,23], nanosheets [22], and even to discover new crystallographic phases [24]. However, these processes do not provide sufficiently-narrowed size distributions yet.…”