Abstract
Carbon nanospheres with a high Brunauer–Emmett–Teller (BET) specific surface area were fabricated via the pyrolysis of polyacrylonitrile–poly(methyl methacrylate) (PAN–PMMA) core–shell nanoparticles. Firstly, PAN–PMMA nanoparticles at high concentration and low surfactant content were controllably synthesized by a two-stage azobisisobutyronitrile (AIBN)-initiated semicontinuous emulsion polymerization. The carbon nanospheres were obtained after the PAN core domain was converted into carbon and the PMMA shell was sacrificed via the subsequent heat treatment steps. The thickness of the PMMA shell can be easily adjusted by changing the feeding volume ratio (FVR) of methyl methacrylate (MMA) to acrylonitrile (AN). At an FVR of 1.6, the coarse PAN cores were completely buried in the PMMA shells, and the surface of the obtained PAN–PMMA nanoparticles became smooth. The thick PMMA shell can inhibit the adhesion between carbon nanospheres caused by cyclization reactions during heat treatment. The carbon nanospheres with a diameter of 35–65 nm and a high BET specific surface area of 612.8 m2/g were obtained from the PAN–PMMA nanoparticles synthesized at an FVR of 1.6. The carbon nanospheres exhibited a large adsorption capacity of 190.0 mg/g for methylene blue, thus making them excellent adsorbents for the removal of organic pollutants from water.
Highlights
Due to their high specific surface area, chemical inertness, good mechanical stability and unique electrical properties, carbon nanospheres have numerous potential applications in nanocomposites [1], gas storage [2], lithium batteries [3,4,5], fuel cells [6,7], supercapacitors [8,9], catalysis carriers [10,11], drug delivery [12,13] and adsorption [14,15]
To realize the efficient and controlled fabrication of PAN-based carbon nanospheres from a PAN–poly(methyl methacrylate) (PMMA) nanoparticle precursor via the pyrolysis method, one should first realize the controlled and efficient fabrication of PAN nanoparticles and distribution curve shift to larger diameters. This indicates the formation of a PMMA outer layer on the PAN seed, as well as the fact that the thickness of the PMMA outer layer can be adjusted via varying the feeding monomer ratio
By a combination of emulsion polymerization and pyrolysis, we demonstrated a facile and efficient route to fabricate discrete, PAN-based carbon nanospheres
Summary
Due to their high specific surface area, chemical inertness, good mechanical stability and unique electrical properties, carbon nanospheres have numerous potential applications in nanocomposites [1], gas storage [2], lithium batteries [3,4,5], fuel cells [6,7], supercapacitors [8,9], catalysis carriers [10,11], drug delivery [12,13] and adsorption [14,15]. A PAN nanolatex with an average diameter of 96 nm and a polydispersity index of 0.03 at an AN concentration of 100 g/L (based on the volume of water) and an SDS content of 3.3% (based on the weight of monomers) was firstly fabricated by the novel emulsion polymerization method, and used as the seed for the preparation of PAN–PMMA latex.
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