Issue 10, 2015

Tuning the singlet-triplet energy gap: a unique approach to efficient photosensitizers with aggregation-induced emission (AIE) characteristics

Abstract

The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states (ΔEST), which offers the opportunity to improve the yield of the triplet excited state. Herein, we demonstrate that modulation of the excited states is also an effective strategy to regulate the singlet oxygen generation of photosensitizers. Based on our previous studies that photosensitizers with aggregation-induced emission characteristics (AIE) showed enhanced fluorescence and efficient singlet oxygen production in the aggregated state, a series of AIE fluorogens such as TPDC, TPPDC and PPDC were synthesized, which showed ΔEST values of 0.48, 0.35 and 0.27 eV, respectively. A detailed study revealed that PPDC exhibited the highest singlet oxygen efficiency (0.89) as nanoaggregates, while TPDC exhibited the lowest efficiency (0.28), inversely correlated with their ΔEST values. Due to their similar optical properties, TPDC and PPDC were further encapsulated into nanoparticles (NPs). Subsequent surface modification with cell penetrating peptide (TAT) yielded TAT–TPDC NPs and TAT–PPDC NPs. As a result of the stronger singlet oxygen generation, TAT–PPDC NPs showed enhanced cancer cell ablation as compared to TAT–TPDC NPs. Fine-tuning of the singlet-triplet energy gap is thus proven to be an effective new strategy to generate efficient photosensitizers for photodynamic therapy.

Graphical abstract: Tuning the singlet-triplet energy gap: a unique approach to efficient photosensitizers with aggregation-induced emission (AIE) characteristics

Supplementary files

Article information

Article type
Edge Article
Submitted
12 Maijs 2015
Accepted
04 Jūl. 2015
First published
06 Jūl. 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2015,6, 5824-5830

Tuning the singlet-triplet energy gap: a unique approach to efficient photosensitizers with aggregation-induced emission (AIE) characteristics

S. Xu, Y. Yuan, X. Cai, C. Zhang, F. Hu, J. Liang, G. Zhang, D. Zhang and B. Liu, Chem. Sci., 2015, 6, 5824 DOI: 10.1039/C5SC01733E

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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