Investigations of hollow carbon nanoshell structures

Abstract

Discrete, uniform 650 °C, in situ inside a transmission electron microscope with a microelectromechanical system (MEMS) system is presented, with the size of the resultant HCNS being slightly larger than that of the AgNP template. Further, ex situ heating of AgNP on carbon nanotube supports has revealed the defining features of these very stable HCNS structures: hollow interiors and very thin graphitised, yet highly disordered walls. A formation mechanism is proposed for the thermal transformation of stabilising layer alkane thiol molecules during HCNS synthesis, occurring in advance of AgNP template removal. Accordingly, the AgNP core acts both as a physical template for HCNS and catalyses the graphitisation of carbon. It is considered that one-step thermal processing of thiol stabilised AgNP provides for excellent size control of the HCNS product, via appropriate AgNP template selection. In particular, a fast heating rate is found to be crucial for the formation of well-defined graphitic <10 nm sized HCNS, whilst intermediate and slow heating rates give rise to products that reflect competition between HCNS formation and AgNP ripening. Significantly, a range of AgNP starting materials, stabilised by ligands containing F or N, also produce similar HCNS following a fast rate of heating , reflecting starting material morphology . The presence of F in HCNS has been demonstrated, but evidence for inclusion of N is more tentative. However, the addition of heteroatoms to AgNP presents challenges for sample handling due to aggregation and changes to the dispersion of AgNP in solvents