Substrate-free bismuth nanofilms with an average thickness of 0.6 nm (sigma = +/- 14.1%) and monodisperse layered Bi nanorhombuses with an average edge length of 21.5 nm (sigma = +/- 14.7%) and thickness of 0.9 nm (sigma = +/- 25.8%) have been successively synthesized by structure-controlling solventless thermolysis from a new layered bismuth thiolate precursor with a 31.49 angstrom spacing. The morphologies result from self-control at an atomic level by the layered Bi(SC12H25)(3) crystal structure. The formation of the Bi nanofilm intermediate provides significant substantiation for this synthesis method, and detailed evidence on the conversion progress has been obtained. Both the films and the rhombuses have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), high-resolution TEM (HRTEM), and atomic force microscopy (AFM) measurements. Special UV-vis electronic absorption spectra of the nanoproducts have been studied.