The synthesis of multilayer van der Waals (vdW) film materials has attracted considerable interest in both fundamental and applied research. Recently, methods for synthesizing multilayer graphene films or graphite on single-crystal nickel foils are developed. However, the chemical vapor deposition (CVD) synthesis of thick-layer graphene films or graphite (TLG) on copper substrates remains a significant challenge due to the self-limiting growth phenomenon. In this study, a novel method to grow TLG on copper substrates by controlling the silicon additive is presented. The as-grown TLG exhibits high quality, with controllable thickness from a few layers to tens of nanometers. The growth of TLG films is achieved by the synchronous growth of multilayer graphene islands on a silicide copper surface, which is likely to be in a liquid state according to the Cu-Si phase diagram. On the Cu-Si surface, all graphene layers grow synchronously, circumventing the self-limiting mechanism and the antiwedding cake growth or wedding cake mode of van der Waals material growth. Based on this synchronous growth mode, the thickness of TLG can be precisely controlled, ranging from a few to tens of nanometers. The study provides a facile and scalable way to synthesize high-quality thick vdW films for various applications.
Silica intercalated graphene-silica composites (G/SiO 2 ) were prepared by one-step hydrothermal method. In the previously reported one-step method for synthesizing G/SiO 2 composites (eg. Bull. Mater. Sci., 37 (2014), 589–595; Applied Surface Science 259 (2012), 566–573), graphene needs to be synthesized first and then used to prepare G/SiO 2 composites. In this work, neither the preparation of graphene nor the use of graphite as a carbon source is required for the preparation of G/SiO 2 composites. Instead, organic solvent (such as toluene, xylene, mesitylene, n-hexane, n-heptane, and cyclohexane) was directly used as the carbon source, and the growth and recombination of graphene and SiO 2 were achieved simultaneously through a one-step hydrothermal method. In a hydrothermal reaction vessel, the mixture consisting of organic solvent, TEOS, H 2 O, and surfactant was uniformly stirred, and then reacted at 160 °C for 4 h to prepare G/SiO 2 composite. The influence of the type of organic solvent, hydrothermal reaction temperature, and calcination temperature on the structure of G/SiO 2 composites were studied. The morphology and structure of G/SiO 2 composites were characterized by FESEM, TEM, and Raman. The formation mechanism of G/SiO 2 composite was proposed. G/SiO 2 composite was then grown directly on the SiO 2 spheres and used as stationary phase for high performance liquid chromatograph separation. Mixture of hydrocarbons was well separated under reversed phase condition.
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