Developing efficient heavy-atom-free photosensitizers applicable to TTA upconversion in polymer films

Jiang, Peng; Guo, Xin; Jiang, Xinpeng; Zhao, Dahui; Ma, Yuguo

doi:10.1039/c5sc03245h

Cited by 115 publications

(105 citation statements)

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“…66 Recent advances in synthetic and theoretical approaches may open up new avenues to solve these problems by using upconverting molecules for PDT study. 67, 68 The upconverting range of UCNPs can be easily modulated from NIR to shorter NIR, NIR to visible, or NIR to ultraviolet (UV) emission through engineering the synthetic methods, either by dopant control or by formation of core-shell structure. Moreover, light emitted by UCNPs is considered to be nonblinking and nonbleaching, less light scattering, and capable of deep tissue penetration because the excitation in the NIR region is within the optical ‘transparency’ window of biological tissues.…”

Section: Depth Penetrationmentioning

confidence: 99%

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

et al. 2016

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Reactive oxygen species (ROS)-mediated mechanism is the major cause underlying the efficacy of photodynamic therapy (PDT). The PDT procedure is based on the cascade of synergistic effects between light, photosensitizer (PS) and oxygen, which greatly favor the spatiotemporal control of the treatment. This procedure has also evoked several unresolved challenges at different levels including (i) limited penetration depth of light restricts traditional PDT to only superficial tumours; (ii) oxygen reliance deprives PDT treatment of hypoxic tumours; (iii) light could complicate the phototherapeutic outcomes due to the concurrent heat generation; (iv) specific delivery of PSs to sub-cellular organelles for exerting effective toxicity remains an issue; and (v) side effects by undesirable white-light activation and self-catalysation of traditional PSs. Recent advances in nanotechnology and nanomedicine have provided new opportunities to develop ROS-generating systems through photodynamic or non-photodynamic procedures while tackling the challenges of current PDT approaches. In this review, we summarize the current status and discuss the possible opportunities of ROS generation for cancer therapy. We hope this review will spur pre-clinical research and clinical practice for ROS-mediated tumour treatment.

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Section: Depth Penetrationmentioning

confidence: 99%

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

et al. 2016

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“…To this end, we introduced a similar annihilator‐appending strategy as used for metal complex sensitizers to the TADF systems, that is to covalently ligate an annihilator as the intramolecular energy acceptor unit (e.g., DBP) to TADF molecule, such as 4CzPN ( Figure ) . In contrast to 4CzPN, DBP‐tethered 4CzPN‐DBP showed only very weak fluorescence upon photoexcitation, suggesting more stabilized triplet state of the bichromophoric molecule.…”

Section: Metal‐free Organic Triplet Photosensitizersmentioning

confidence: 99%

“…The covalently tethered DBP (red) is critical for achieving superior TTA UC performance especially in the solid matrix, essentially by suppressing the reverse ISC and more effectively transferring triplet excitons to free DBP emitters (blue). Reproduced with permission . Copyright 2016, Royal Society of Chemistry.…”

Section: Metal‐free Organic Triplet Photosensitizersmentioning

confidence: 99%

“…Besides, organic dyes comprising a spin convertor (such as C 60 ) with inherent ISC property can also be used as sensitizers . More recently, a novel class of heavy‐atom‐free sensitizers emerges, known as thermally activated delayed fluorescence (TADF) molecules . Taking advantage of rationally designed chemical structures, small Δ E ST and highly efficient ISC are the distinctive features of these promising triplet sensitizers.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequent intermolecular TTET to the free annihilator may take place with both the sensitizer and tethered annihilator. The current contribution will focus on the most recent research efforts and progress made with designing new TTA UC sensitizers, particularly those emerged in the past 5 years. All prior relevant work and studies are not comprehensively covered herein, since they have been elegantly summarized by previous reviews …”

Section: Introductionmentioning

confidence: 99%

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New Bichromophoric Triplet Photosensitizer Designs and Their Application in Triplet–Triplet Annihilation Upconversion

Guo

Liu

Chen

et al. 2018

Advanced Optical Materials

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the distinctive advantage of using noncoherent light as the excitation source. Hence, the TTA-based photon upconversion (UC) is promised with a wider range of applications, such as harvesting the much abundant low-energy photons in the solar spectral irradiation and converting them to usable photons in photovoltaic devices. [4,5] Moreover, the development of TTA UC is also driven by the potential applications pertinent to photocatalysis and bio-technologies. [6][7][8][9] The two main functional components in a TTA UC system are the triplet photosensitizer and annihilator, the latter of which also serves as the emitter. While only a limited number of annihilators have so far been identified capable of efficient TTA upconverted emission, remarkable progress has been made with the design and investigation of photosensitizers in the past decade. A range of transitionmetal complexes and organic structures have been studied as potent photosensitizers. By virtue of all the various sensitizers that have been developed, a wide range of photon energy, ranging from visible to near-infrared, can now be used and upconverted by the TTA systems reported in the literature. [10,11] Furthermore, different types of materials, including various solvents, gels, polymers, have been employed as matrices to perform TTA UC, and even matrix-free conditions have been reported. [11][12][13][14][15] Mechanism of TTA UCThe streamlined mechanistic steps in a TTA UC are summarized in Figure 1. [16] In a typical bi-component system, upon absorbing a low-energy photon, the photosensitizer is excited into a singlet excited state before undergoing inter-system crossing (ISC) to the triplet state. Then, an intermolecular triplet-triplet energy transfer (TTET) takes place between the excited sensitizer and a nearby annihilator, regenerating the ground-state sensitizer along with an annihilator triplet. Since the annihilators are usually organic hydrocarbon molecules with spin-forbidden triplet-to-singlet relaxations, long-lived annihilator triplets thus accumulate over time, until bimolecular triplet-triplet annihilation takes place and generates a As indispensable molecular components, photosensitizers play a crucial role in determining the quantum efficiency of triplet-triplet annihilation upconversion (TTA UC). This emergent technology has attracted great attention in recent years for realizing large anti-Stokes shifts with noncoherent excitation sources. In a typical TTA UC, low-energy photons are first harvested by the photosensitizers, which upon intersystem crossing (ISC) undergo triplettriplet energy transfer (TTET) to emitters (i.e., annihilators). Following the bimolecular TTA among the emitters, high-energy photons are given off by the singlet excited state of the emitters. Apparently, the efficiencies of photon absorption, ISC, and TTET are all dependent on the sensitizers. With a Dextertype ET mechanism requiring collisional interactions, a long triplet lifetime of the energy donor (photosensitizer) is evidently favorable for enhancing ...

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Highly Efficient Triplet‐Triplet‐Annihilation Upconversion Sensitized by a Thermally Activated Delayed Fluorescence Molecule in Optical Microcavities

Han

Zhu

Ouyang

et al. 2021

Adv Funct Materials

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Triplet-triplet-annihilation (TTA) upconversion sensitized by a new thermally activated delayed fluorescence (TADF) molecule, BTZ-DMAC-4Br, is investigated in whispering gallery mode (WGM) microcavities made of toluene solutions filled into quartz capillaries. Since the utilization of the excitation light is improved in WGM microcavities through total internal reflection, the upconversion efficiency is enhanced greatly and an upconversion quantum yield of 24.6% is observed, which is a dozen times higher than that measured in conventional cuvettes. To the best of knowledge, this is the highest upconversion efficiency achieved in TADF sensitized TTA systems. Not only is a new material designed, but also the results provide a novel way to improve the TTA upconversion performance by utilizing the optical cavity effect, and the TTA microcavities may be used to construct highly efficient and low-threshold photonic devices in many applications.

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Developing efficient heavy-atom-free photosensitizers applicable to TTA upconversion in polymer films

Abstract: Heavy-atom-free triplet photosensitizers are developed and visible-to-ultraviolet photon upconversion is realized via triplet–triplet annihilation.

Cited by 115 publications

References 48 publications

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

New Bichromophoric Triplet Photosensitizer Designs and Their Application in Triplet–Triplet Annihilation Upconversion

Highly Efficient Triplet‐Triplet‐Annihilation Upconversion Sensitized by a Thermally Activated Delayed Fluorescence Molecule in Optical Microcavities

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