<p>This work reports the development of a 3D-printable photopolymerizable nanocomposite containing upconversion nanoparticles for in situ UV generation and a Proof of Concept (PoC) with the aim of establishing, as a parameter, photopolymerization monitored by ATR-FTIR spectroscopy to assess the potential possibility of IR-activated decontamination of 3D printed surfaces. This PoC is based on the equivalence between the UV dose values required for photopolymerization and the dose value required for viral inactivation, as reported in the literature. The process involved (1) the synthesis and characterization of NaGdF₄:Yb³⁺:Tm³⁺ upconversion nanoparticles (UCNPs) as the optically active phase and (2) the incorporation of these nanoparticles into a photopolymerizable resin. The resulting upconversion photopolymerizable nanocomposite (UCPPNC) was 3D-printed via masked stereolithography (MSLA) and exhibited UV emission under 980&#xa0;nm near-infrared (NIR) excitation through a five-photon upconversion mechanism. Real-time ATR-FTIR spectroscopy of samples under 980&#xa0;nm pumping showed that the UV radiation produced in situ by the incorporated UCNPs was sufficient to enable photopolymerization of the surrounding resin. Thus, the PoC demonstrated, through an indirect but relevant correlation, the potential of UCPPNCs as an IR-activated decontaminable printable material. This nanoparticle-enabled material may offer a safer and more energy-efficient alternative to conventional UV disinfection methods, enabling spatially controlled inactivation of pathogens, while its compatibility with additive manufacturing supports rapid prototyping of customized and application-specific designs for healthcare, public infrastructure, and wearable technologies. Finally, the proposed PoC allowed us to pre-evaluate the material’s potential for IR-activated decontamination, establishing a biological testing-free process for preliminary analysis.</p> Graphical Abstract <p></p>