The morphology, microstructure and chemical composition of soot particles emitted directly from biofuel cook stoves have been studied by using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ion beam analysis (IBA) techniques. Freshly emitted soot particles were collected using an eight stage cascade impactor that separates particles according to their size. The particulate matter is impacted on thin aluminum foil and copper grids for Transmission Electron Microscope. The analysis of HRTEM micrographs revealed the nanostructure and the particle size of soot chain. Results from the border-based fractal dimension indicated that main morphological differences observed in soot particles perhaps are associated to cook stove chamber design. XPS analysis shows that particles are mainly composed by carbon and oxygen. The XPS C-1s spectra show carbon with three peaks corresponding to sp(2), spa(3) hybridization and carbon oxygen bond. Additionally, we determined the areal density (atoms/cm(2)) of the soot films and the purity of the substrates by means of IBA techniques. (C) 2016 Elsevier Ltd. All rights reserved.