Lanthanide‐Doped Nanoparticles for Near‐Infrared Light Activation of Photopolymerization: Fundamentals, Optimization and Applications

Abstract

Photopolymerization refers to a type of polymerization process in which light is utilized as excitation source to initiate polymerization of monomers and oligomers. Despite great progress, photopolymerization is typically induced by ultraviolet or visible light, which still greatly restrains its applications. Upconversion nanoparticles (UCNPs) represent a class of optical nanomaterials that are able to convert low‐energy near‐infrared (NIR) light into high‐energy ultraviolet (or visible light) emissions. In this context, UCNP‐assisted photopolymerization has recently attracted extensive attentions due to its unique advantages. In this account, recent advances in the fundamentals, optimization and emerging applications of UCNP‐based photopolymerization are reviewed. Fundamental theories of upconversion luminescence and photopolymerization will be introduced first. Various optimization approaches to improve UCNP‐assisted photopolymerization are then summarized, followed by diverse emerging applications. Challenges and future perspectives in this area will be provided as a conclusion.

Exploiting the upconversion luminescence, Lewis acid catalytic and photothermal properties of lanthanide-based nanomaterials for chemical and polymerization reactions

“…Apart from the energy transfer upconversion mechanism, other explanations used to understand the anti-Stokes shift in emission include excited state absorption, photon avalanche, cooperative upconversion and energy migration-mediated upconversion. 1,6,12,77…”

“…Compared to conventional photopolymerization using direct UV/visible light, UCNC-assisted polymerization has several advantages including easier medical treatment procedures (e.g., treatment of carious lesions), enhanced polymerization rate, improved degree of monomer conversion, and increased polymerization depth. [77][78][79][80][81] The combination of a UCNC and a photoinitiator allows emitted upconverted photons to excite the latter to produce active species that initiate the polymerization reaction. For example, Liu et al performed the polymerization of epoxy acrylate by coupling NaYF 4 :Yb 3+ ,Tm 3+ UCNC and the photoinitiator Irgacure 784.…”

Upconversion nanoparticles and its based photodynamic therapy for antibacterial applications: A state-of-the-art review

“…In the case of cooperative sensitization, two excited ions (ions 1 and 2) absorb one photon to generate their excited levels and then together, transfer the energy to another ion (ion 3) to upgrade its excited-state level. In the case of cooperative luminescence, two excited interacting ions (ions 1 and 2) could absorb one photon and cooperate in producing the emission ( Li et al, 2020c ; Kandoth et al, 2021 ; Li et al, 2021 ).…”

Triplet‐Triplet Annihilation Up‐Conversion Luminescent Assisted Free‐Radical Reactions of Polymers Using Visible Light

“…Recently, another effective way is reported, which directly solves light penetration issue and increases photoinitiated reaction depth based on up-conversion (UC) materials that absorb low-energy photons and convert them into high-energy ones for emission. [22][23][24][25] UC is an anti-Stokes shift process, [26] and UC materials are considered to be an effective way to increase photoinitiated polymerization depth, [27,28] i.e., they act as internal light source that converts long-wavelength light with strong penetrating ability into high-energy short-wavelength light that is absorbed by photosensitive monomers (prepolymers) or photo-initiators. [29][30][31] Besides, UC-assisted photoinitiated free-radical reactions utilize commercially available resins and photo-initiators without further modifications, [32] which is beneficial for industry and engineering.…”