Plasmon enhanced upconverting core@triple-shell nanoparticles as recyclable panchromatic initiators (blue to infrared) for radical polymerization

Abstract

Plasmonic enhanced upconverting nanoparticles were constructed for visible to near-infrared light-driven photo-polymerization.

Tunable Quantum Photoinitiators for Radical Photopolymerization

“…Upconverting nanoparticles (UCNPs) are luminescent materials that are capable of emitting higher energy, lower wavelength photons on absorption of lower energy, higher wavelength incident light [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. This photophysical phenomenon, which is referred to as photon upconversion, is based on an anti-Stokes process and involves sequential absorption of two or more low-energy photons, which enables the population of real, intermediate excited electronic states, followed by emission of a single high-energy photon.…”

“…Liu et al reviewed several strategies to increase up conversion luminescence efficiency, such as energy transfer modulation, surface passivation, host lattice manipulation, photonic crystal engineering, broadband sensitization, and surface plasmonic coupling. Rationally designed nanohybrids of UCNPs with enhanced photocatalytic activity behave as effective panchromatic radical photoinitiators [ 31 , 32 , 33 , 34 ].…”

“…Loir et al indicated that two pathways exist for initiation in quantum PIs, which involve surface mediated hole transfer ( Figure 1 ) [ 10 ]. Typical quantum PIs can be classified as semiconductor nanoparticles (NPs), such as TiO 2 , ZnO, and CdS NPs [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]; hybrid photoinitiators, including composites of metal nanoparticles (MNPs)/silanized metal (organic PIs, MNPs), fluorescent dyes, oligomeric silsesquioxane, and parent PIs, [ 17 ] semiconductor NPs (metal/graphene oxide) [ 18 , 19 , 20 , 21 , 22 , 23 ], and organometallic nanoparticles; panchromatic photoinitiators, namely upconverting nanoparticles (UCNPs) [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ] and plasmonic nanoparticle composites (e.g., Ag@SiO 2 @UC@BFO–Au core@triple-shell); near-infrared photoinitiators, such as luminescent lanthanides (e.g., Ln 3+ , Yb 3+ , Er 3+ , and Ho 3+ ) and doped nanomaterials in a crystalline host lattice (NaYF 4 ); [ 31 ] magnetic nanoparticles, such as Fe 2 O 3 ; and metal core-shell nanoparticles (e.g., Ag@AgCl nanocubes) [ 35 , 36 ]. Figure 2 describes the polymerization of acrylic acid sodium (AAS) using the Ag@SiO 2 @UC@BFO-Au photoinitiator.…”

“…In general, nanoscale PIs are efficient for photo-curable polymerization applications in aqueous solutions and ultraviolet light (UV)-dependent stereolithography 3D printing [ 17 , 25 ]. They have superior conversion rates, a low risk of migration, exceptional cross-linking behavior, and good compatibility with aqueous media, owing to a large absorbance cross-section in UV–Vis region [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. Quantum PIs enable the migration issue to be minimized due to their higher molecular weights.…”

Recent advances on pyrene-based photoinitiators of polymerization

“…[236] Panchromatic photoinitiators are actively researched in photopolymerization as these compounds exhibit an almost constant sensitivity to light over a wide range of absorption and thus do not require a specific wavelength for photoinitiation. [237][238][239][240] Considering that Pyr_48 is panchromatic, polymerization processes could be initiated with seven different LEDs (365, 395, 405, 457, 473, 532 and 635 nm). While using the threecomponent system Pyr_48/Iod/NVK (1%/2%/3%, w/w), final conversions ranging between 60 % (LED at 532 nm) to 95% (LED at 365 nm) could be determined (See Figure 19), demonstrating the versatility of this photochrome.…”