Fluorinated Surface of Carbon Nanotube Buckypaper for Uniform Growth of CdS Nanoparticles

Interfacial interactions between CdS species and multiwalled carbon nanotubes (MWCNTs) determine the architecture and optical characteristics of CdS/MWCNT hybrids. The effect of fluorinated surface of MWCNT buckypaper on the decoration with CdS nanoparticles from an ammonia solution of cadmium(II) chloride and thiourea has been studied. Scanning electron microscopy showed that the fluorinated carbon surface provides more dense growth and uniform distribution of CdS nanoparticles. X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies revealed a partial defluorination of the nanotubes and the formation of elemental sulfur as a result of a joint action of thiourea and ammonia. The carbon atoms freed of fluorine were found from density functional theory calculations to be active sites for attachment of Cd(II) complexes present in the chemical bath and subsequent growth of CdS nanoparticles. The obtained hybrid possesses dual photoluminescence from fluorinated MWCNTs and CdS nanoparticles. Under applied electric field, it emits blue light that is possible only for very small CdS nanocrystals. This work provides a concept for fabrication of CNT-based hybrid structures with the high density of semiconducting nanoparticles for optoelectronic applications.