Nanoparticles built up from polythiophenes act as photosensitizers without embedding any additional chromophores. The self-organized water-soluble nanoparticles in this work are made from polythiophene precursors with alkyl side chains which were combined with diphosphatidylcholine-polyethylene glycol in different mass ratios. The fluorescence and singlet oxygen quantum yields of such nanoparticles can be tuned by varying the mass ratio of the two components. Two unique properties of these polymeric photosensitizers result in special singlet oxygen kinetics. First, the backbone orientation of the polythiophene influences the probability of triplet excitons, which have a high mobility across all the nanoparticle and, second, oxygen can diffuse in and out of the polymeric photosensitizer. Therefore, most of the singlet oxygen is generated inside the nanoparticle, close to the surface, soon after oxygen diffuses in. After generation, the majority of the singlet oxygen diffuses out of the nanoparticle. Using highly sensitive time- and spectrally resolved singlet oxygen phosphorescence detection, the oxygen diffusion can be confirmed, and the observed kinetics and quantum yield variations can be explained based on the polymer–semiconductor model. Whenever singlet oxygen kinetics in polymeric nanostructures are investigated, such oxygen diffusion effects have to be taken into account.
Singlet oxygen is well known as the main mediator of photodynamic therapy. Therefore, great efforts are being made to detect singlet oxygen in many different biological environments. The most promising method is the time-resolved luminescence detection via its very weak nearinfrared phosphorescence.However, in many biological environments these time-resolved measurements suffer from signal artifacts at short times (within the first 2 µs) after the excitation pulse. Neither the origin nor the kinetics of these disturbance signals have yet been successfully elucidated. Up to now, no way for eliminating them has been developed, be it mathematical or experimental.This work reports about a method for discrimination of the singlet oxygen phosphorescence from a disturbed signal by spectrally resolved measurements. We use a tiltable interference filter as an experimentally efficient and comparably cheap method to conduct highly sensitive time-and spectrally resolved luminescence measurements, inherently suitable for the future application in biological systems.We use Rose Bengal in water as an example system. It generates singlet oxygen at high quantum yield and shows additional luminescence emissions. The complex luminescence of Rose Bengal is treated as the disturbance signal. The isolation of the singlet oxygen phosphorescence by a fitting algorithm is demonstrated.
No abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.