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Novel technique to produce porous thermochromic VO 2 nanoparticle fi lms using gas aggregation sourceJan Prokeš 1 , Tereza Košutová 2 , Jaroslav Kousal 1 , Anna Kuzminova 1 & Ond?ej Kylián 1?Vanadium dioxide (VO 2 ) is a phase transition material that undergoes semiconductor-to-metal transition at the temperature of about 68 °C. This extraordinary feature triggered intensive research focused on the controlled synthesis of VO 2 . In this study, we introduce and investigate an original linker- and solvent-free strategy enabling the production of highly porous VO 2 nanoparticle-based fi lms. This technique combines a gas-phase synthesis of vanadium nanoparticles and their subsequent atmospheric pressure thermal oxidation. It is shown that the thermochromic behaviour of such produced nanomaterial is at the fi xed oxidation temperature strongly dependent on the oxidation time. Concerning this, it was found that there exists an optimal oxidation time (60 s in our study) that assures the production of crystalline VO 2 nanoparticles with the highest, reproducible and temporally stable semiconductor-to-metal transition with the resistive switching ratio close to 2 orders of magnitude and dramatic switching of optical properties in the near infra-red spectral region.Keywords Vanadium dioxide, Nanoparticles, Resistive switching, Th ermochromic materials, Gas aggregation sourceVanadium dioxide (VO 2 ) has been among the most studied metal oxides for over half a century. Th e interest in VO 2 is primarily due to its extraordinary properties, namely, its semiconductor-to-metal transition (SMT). Th is phenomenon, fi rst reported by Morin in 1959 1 , occurs at a critical temperature T c of about 68 °C and is accompanied by a fi rst-order structural phase transformation from a monoclinic to a tetragonal structure 2 . In addition, the SMT causes a drastic change in optical properties; while VO 2 is transparent to near-infrared light at temperatures below T c it becomes translucent above T c in this spectral range. Th ese characteristics paved the way for the use of VO 2 in an impressive range of applications such as smart windows that regulate the intensity of transmitted light in response to environmental temperature 3–8 , smart thermal radiator devices for thermal control in space 9,10 , thermoregulating textiles 11–13 , optical switches and plasmonic devices 14–16 , micro-actuators or solid engines 17–19 , micro-bolometers 20 , or memristive devices including the option for neuromorphic computing 21–23 . Naturally, the performance of VO 2 is of t en linked with its structure (e.g., doping 24–26 ) or size 27–29 . Concerning the latter, many of the aforementioned applications require VO 2 with dimensions in the range of nanometres. Th is triggered the development of strategies for synthesising vanadium dioxide nanomaterials in the form of nanowires, nanorods, thin fi lms or nanoparticles (NPs) that are commonly based on chemical processes such as sol-gel deposition, chemical vapour deposition, atomic-layer deposition, or using physical processes such as pulsed-laser deposition or sputtering (e.g., reviews 3,30,31 ).For instance, magnetron sputtering followed by annealing of deposited fi lms was used to produce nanostructured thermochromic VO 2 fi lms by Lu and Hsueh 32 or Geng et al. 33 . A similar approach was also employed by Long et al. 34 , who used co-sputtering of poly(tetraf l uoroethylene) and VO 2 combined with a post-annealing step. Th is self-template process resulted in the formation of VO 2 coatings composed of irregularly shaped structures. Template-free surface-patterning method to prepare structured monolayer VO 2 fi lms was used by Liu et al. 35 and Li at al 36 . In this case, the suitable precursor-containing solution was spin-coated onto a substrate and annealed. Although the aforementioned techniques allow for the facile production of VO 2 nanostructures they are in general suitable solely for the synthesis of surface VO 2 arrays/patterns and not VO 2 porous coatings. To overcome this limitation, another strategy may be used that is based on the synthesis of NPs-based stacks. Th is approach was recently introduced by Dumas-Bouchiat et al. 37 . Th ese authors combined the synthesis of metallic vanadium NPs by means NPs source that utilized pulsed laser and post-annealing of such produced NPs in a well-controlled atmosphere.1 Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University, V Holešovi?kách 2, 180 00 Prague 8, Czech Republic. 2 Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague, Czech Republic. ? email: ondrej.kylian@matfyz.cuni.czOPENScientif i c Reports | (2025) 15:1755 1 | https://doi.org/10.1038/s41598-025-86272-9www.nature.com/scientificreports