Photon upconversion (UC) from near-infrared (NIR) light to visible light has enabled optogenetic manipulations in deep tissues.H owever,m aterials for NIR optogenetics have been limited to inorganic UC nanoparticles.Herein, NIR-light-triggered optogenetics using biocompatible,organic TTA-UC hydrogels is reported. To achieve triplet sensitization even in highly viscous hydrogel matrices,aNIR-absorbing complex is covalently linked with energy-pooling acceptor chromophores,w hichs ignificantly elongates the donor triplet lifetime.T he donor and acceptor are solubilized in hydrogels formed from biocompatible Pluronic F127 micelles,a nd heat treatment endows the excited triplets in the hydrogel with remarkable oxygen tolerance.Combined with photoactivatable Cre recombinase technology,N IR-light stimulation successfully performs genome engineering resulting in the formation of dendritic-spine-like structures of hippocampal neurons.

Efficient NIR-to-blue photon upconversion was realized for the first time by exploiting sensitizer S–T transition and achieved the largest anti-Stokes shift of 0.97 eV.

Triplet dynamic nuclear polarization (triplet-DNP), a method to enhance nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) sensitivity using photoexcited triplet electrons, has great potential to hyperpolarize nuclear spins at room temperature. Since the first report of room-temperature triplet-DNP in 1990, pentacene has been the only and best option of triplet polarizing agent. However, the poor air stability of pentacene has severely limited the applicability of triplet-DNP. We report the first example of polarizing agents with significant air stability as well as high polarizing ability comparable to pentacene. The introduction of electron-withdrawing diaza-substitution to pentacene and tetracene reduces the lowest unoccupied molecular orbital level and endows much improved stability under the ambient conditions. Importantly, the diaza-substituted pentacene and tetracene offer similar, or even slightly better, 1H NMR signal enhancement compared with pentacene in the prototypical triplet-DNP test using p-terphenyl crystals. This work removes one of the largest obstacles toward the application of triplet-DNP for the hyperpolarization of biological molecules.