Generation of open-ended, worm-like and graphene-like structures from layered spherical carbon materials

Abstract

A study of the effects of size dispersion of Au@SiO 2 spheres and silica sphere templates for the synthesis of hollow carbon structures was evaluated using a chemical vapor deposition (CVD) nanocasting method. The diameter of the template, the presence of the gold nanoparticles and the polyvinylpyrrolidone (to cap the Au particles) were found to determine the size, thickness and shape of the synthesized carbon nanostructures. The Au@monodispersed small-sized silica sphere (80-110 nm) template covered with carbon followed by removal of silica produced broken hollow carbon spheres, whereas an equivalent Au@monodispersed large-sized silica sphere (110-150 nm) template produced hollow carbon spheres with a complete carbon shell. Monodispersed and polydispersed pristine silica spheres without Au produced hollow carbon spheres with complete and deformed carbon shells, respectively. Polyvinylpyrrolidone addition to polydispersed SiO 2 spheres, followed by carbonization with toluene (1 h) and SiO 2 removal, produced wormlike carbon structures. Carbonization (and SiO 2 removal) of Au@polydispersed silica spheres for a short carbonization time (1 h) gave a layered carbon nanosheet while at intermediate and longer carbonization times (2-4 h) gave nanotube-like (or worm-like) carbon structures. Raman spectra confirmed the formation of the graphitic nature of the carbon materials.These results highlight the potential use of Au@carbon coreshell structures for the generation of few layered graphene-like unusual nanostructures. As a proof of concept, the wormlike carbon structures were incorporated in organic solar cells and found to give a measurable photovoltaic response.

Hollow carbon spheres and a hollow carbon sphere/polyvinylpyrrolidone composite as ammonia sensors

“…The SiO 2 spheres and the HCSs were synthesized based on a procedure described elsewhere. 50 The preparation of the HCSs and HCS/PVP solutions using a surfactant dispersion method is described in the ESI † section.…”

“…S1 †). 50 The shell diameter in the pristine HCSs was approximately 18 AE 4 nm due to the use of a short (1 h) carbonization time. The TG-DTG curve of the HCSs shows a small derivative peak between 290 C and 400 C (Fig.…”

Nitrogen-doped hollow carbon spheres as chemical vapour sensors

“…The SiO2 spheres were synthesized following a modified procedure reported elsewhere 17 . Briefly, 180 mL of ethanol, 60 mL of distilled water and 10 mL of NH4OH were mixed in a volumetric flask and stirred for 30 min.…”

“…For instance, the carbon shell thickness that is formed on a template can be controlled by varying the surfactant to precursor ratio 13,14 , the amount of the carbon source 15 and the carbonization time 16 . A longer carbonization time and a larger amount of a carbon source result in the formation of a thicker carbon shell whereas a shorter carbonization time will yield a thinner carbon shell 17 . The change in the HCSs shell thickness can influence their degree of graphitization and the conductivity of the carbon layer 18 .…”

Synthesis of Carbon Nanomaterials from Biomass Utilizing Ionic Liquids for Potential Application in Solar Energy Conversion and Storage

“…Additionally, in another study by Sevilla et al [ 18 ], they synthesized graphitic carbon structures using gluconate dehydrates of iron and cobalt, and reported that iron and cobalt nanoparticles successfully catalyzed the reaction at either 900 or 1000 °C. Different CNMs, i.e., worm-like and broken hollow carbon nanostructures, were synthesized using gold- and silica-containing precursors [ 19 ].…”