Polyamidoamine (PAMAM) dendrimers are used as carriers to deliver complexed Fe(Ill) ions uniformly onto silicon oxide substrates for the formation of iron oxide nanoparticles with,a narrow diameter in the range of 1-2 nm. Chemical vapor deposition (CVD) synthesis with these nanoparticles affords single-walled carbon nanotubes (SWNTs) with a diameter distribution in the range of 1-2 run, much narrower than that for SWNTs grown from commonly used powder-supported catalyst (1-5 nm) and from artificial ferritin derived nanoparticles (1-3 nm). Thus, the current work represents a step further toward the synthesis of monodispersed SWNTs via the approach of chemically controlling the formation of discrete catalyst. nanoparticles.