Construction of Position-Controllable Graphene Bubbles in Liquid Nitrogen with Assistance of Low-Power Laser

Graphene
bubbles (GBs) are of significant interest owing to their
distinguished electrical, optical, and magnetic properties. GBs can
also serve as high-pressure reaction vessels to numerous chemical
reactions. However, previous strategies to produce GBs are relatively
elaborate and random. Therefore, their potential applications are
severely restricted. Here, a facile and effective protocol is proposed
to construct position-controllable GBs in liquid nitrogen (LN) with
the assistance of laser and graphene wrinkles. Specifically, a film
of graphene mounted on a SiO2 substrate (G@SiO2) is subjected to irradiation by a low-power laser in LN and then
many GBs emerge from the surface of G@SiO2. Most impressively,
the domain where GBs arise is the position of the laser beam spot.
Hence, we demonstrated that the high collimation of laser facilitates
the position definition of GBs. The microscopic results indicate that
some GBs split into three parts when they were subjected to irradiation
by an electron. Meanwhile, some GBs degenerate into pores with a diameter
of 500 nm when they are exposed to air. To grasp the properties of
GBs in depth, the molecular dynamics (MD) simulations are performed,
and the corresponding results indicate that temperature has very little
impact on the GBs’ shape. A phase transition process of the
substance inside GBs is also revealed. Moreover, a two-dimensional
(2D) solid nitrogen is discovered by MD simulations. The simplicity
of our protocol paves the way to engineer high-pressure microreaction
vessels and fabricate porous graphene membranes.