Prospects for More Efficient Multi-Photon Absorption Photosensitizers Exhibiting Both Reactive Oxygen Species Generation and Luminescence

Abstract

The use of two-photon absorption (TPA) for such applications as microscopy, imaging, and photodynamic therapy (PDT) offers several advantages over the usual one-photon excitation. This creates a need for photosensitizers that exhibit both strong two-photon absorption and the highly efficient generation of reactive oxygen species (ROS), as well as, ideally, bright luminescence. This review focuses on different strategies utilized to improve the TPA properties of various multi-photon absorbing species that have the required photophysical properties. Along with well-known families of photosensitizers, including porphyrins, we also describe other promising organic and organometallic structures and more complex systems involving organic and inorganic nanoparticles. We concentrate on the published studies that provide two-photon absorption cross-section values and the singlet oxygen (or other ROS) and luminescence quantum yields, which are crucial for potential use within PDT and diagnostics. We hope that this review will aid in the design and modification of novel TPA photosensitizers, which can help in exploiting the features of nonlinear absorption processes.

One‐Photon and Two‐Photon Photophysical Properties of Tetrafunctionalized 5,10,15,20‐tetrakis(m‐hydroxyphenyl)chlorin (Temoporfin) Derivatives as Potential Two‐Photon‐Induced Photodynamic Therapy Agents

“…Future work will, in addition to in vitro and in vivo studies, include development of systems aiming to use the combined effect of the non-linear properties of the compounds described here, together with nanoformulation strategies for application in two-photon induced PDT. 58 It is hoped that the development of DDS using m-THPC derivatives as cross-linkers in polymeric nanoparticles will allow for the excitation of chromophores at longer laser wavelengths, leading to deeper penetration of the treated tissues, and in consequence, better therapeutic response and reduction of side effects related to Foscan treatment.…”

Pr3+ doped NaYF4 and LiYF4 nanocrystals combining visible-to-UVC upconversion and NIR-to-NIR-II downconversion luminescence emissions for biomedical applications

“…54 It should be emphasized that in this case the UVC light is generated as a result of UC by sequential twophoton absorption (excitation using an easily accessible 447 nm CW laser source), which is much more efficient than multi-photon processes used for NIR-to-UVC UCL (excitation with 980 nm) or simultaneous absorption of two photons in nonlinear optical processes. [55][56][57] The observed UVC emission of NaYF 4 :Pr 3+ /Yb 3+ and LiYF 4 :Pr 3+ /Yb 3+ NCs peaks at ca. 275 nm (Fig.…”

Ternary Exciplexes for Enhanced Two-Photon Excited Fluorescence by the Synergy Effect of Dual Reverse Intersystem Crossing Channels

“…In a wide excitation window from 680 to 880 nm, the sample exhibits strong upconversion fluorescence emissions with almost the same waveform and emission peaks at ∼515 nm (Figure a), suggesting effective NLO capability of the ternary 3TPYMB:TAPC:T2T exciplex as expected. Moreover, the wide upconversion fluorescence excitation window of at least 200 nm allows more options for input lasers, which provides more convenience for NLO applications. , It is noted that the upconversion fluorescence spectra show similar waveforms and band peaks to that of the downconversion PL spectrum in Figure b and almost coincide with the upconversion spectra of the TAPC:T2T exciplex (Figure S3a), indicating the same fluorescence mechanism for up- and downconversion fluorescence. We further measured the power dependence of upconversion fluorescence spectra of the ternary 3TPYMB:TAPC:T2T exciplex under the laser excitation of 700 nm.…”