Development of the sensitizer for generating higher-energy photons under diluted condition via the triplet-triplet annihilation-supported upconversion

Micelles Embedded in Multiphasic Protein Hydrogel Enable Efficient and Air-Tolerant Triplet Fusion Upconversion with Heavy-Atom and Spin–Orbit Charge-Transfer Sensitizers

“…The Φ UC of 19.0 ± 0.7%, achieved by the BSA/SDS/ 1 /DPA hydrogel, is currently the highest Φ UC observed in a hydrogel system and it is among the highest Φ UC values reported under aerobic conditions, overall . While 1 gave the highest Φ UC among all of the sensitizers tested in the BSA/SDS hydrogel, most likely because of the higher annihilator concentration and the higher triplet yield brought on by Pd 2+ , − the remaining sensitizers still achieved impressive Φ UC values in their class. A Φ UC of 10.7 ± 0.4% was measured in the BSA/SDS/ 2 /Pery hydrogel, which was higher than the Φ UC reported for 2 /Pery in deaerated toluene, hexane, heptane, and dimethyl sulfoxide .…”

“…First, the Φ PL of the BSA/SDS/ 1 hydrogel, which contained constant [ 1 ] = 21.2 μM and varying [BSA] = 2.6–6.0 mM, was measured (Figure S6). Since the triplet yield of 1 is virtually unity, − the Φ PL of the BSA/SDS/ 1 hydrogel consisted purely of phosphorescence. Therefore, the Φ PL of the BSA/SDS/ 1 hydrogel was regarded as a measure of oxygen protection afforded by varying degrees of BSA network density.…”

“…We need high triplet-yielding sensitizers for TTA-UC to be efficient. In this regard, a majority of reported TTA-UC systems utilize metal-containing sensitizers. − These traditional sensitizers typically benefit from broad absorption profiles, high absorption intensities, and microsecond-scale triplet excited state lifetimes, and their high triplet yields are due to the presence of heavy, paramagnetic metals (e.g., Pd 2+ , Pt 2+ , Zn 2+ , Ru 2+ , and Ir 3+ ). − Metal-containing sensitizers are not ideal because of their high-cost, high-temperature synthesis, which is only complicated by the production of heavy metal waste products that are toxic and difficult to remove. − Alternatively, sensitizers with high triplet yields can be synthesized by incorporating heavy halogens (Br and I) into chromophores, such as boron dipyrromethene (Bodipy) derivatives, but this tends to decrease the triplet excited state lifetime and it can increase the cost of synthesis. − To avoid these problems, recent research efforts have been dedicated to the development of sensitizers with high triplet yields that do not contain heavy atoms. One promising class of completely organic sensitizers is orthogonal donor-acceptor dyads, which efficiently produce triplet excited states via spin–orbit, charge-transfer intersystem crossing (SOCT-ISC) and can be used for applications in TTA-UC. ,− …”

Efficient Red-to-Blue Triplet–Triplet Annihilation Upconversion Using the C70-Bodipy-Triphenylamine Triad as a Heavy-Atom-Free Triplet Photosensitizer

“…During the past two decades, many triplet photosensitizers were synthesized for TTA-UC applications. The earliest photosensitizers were mainly transition metal–organic complexes, such as Ru, Pt, , Pd, Os, , and Ir, in which the metal atom center significantly enhanced spin–orbit coupling (SOC) of chromophores, leading to a high ISC efficiency. After that, some metal-free organic photosensitizers containing Br and I atoms , also showed high ISC effect according to the heavy-atom effect.…”

Charge separation, charge recombination and intersystem crossing in orthogonal naphthalimide–perylene electron donor/acceptor dyad

“…The triplet state can phosphorescence, or initiate energy or electron transfer. Triplet PSs have been widely used in photocatalysis, [4][5][6] photodynamic therapy, [7][8][9][10] photovoltaics, [11] and photon upconversion [12][13][14][15][16][17][18].…”