Rationalizing the Plasmonic Contributions to the Enhancement of Singlet Oxygen Production

Abstract

The strong interaction between plasmonic metal nanoparticles and photosensitizers can significantly amplify their singlet oxygen (1O2) production. However, improving the performance of these hybrid plasmonic nanostructures is hampered by the lack of understanding of how their plasmonic properties impact the enhancement of 1O2 production. Here, we report that a Au core-based nanoparticle can outperform a Ag one. This result is striking as Ag is referred to as a better plasmonic metal than Au and forms the basis of our investigation. We use a novel approach based on a mini meta-analysis to elucidate and quantify the near- and far-field contributions to the plasmon-enhanced 1O2 production by using a highly tunable model hybrid photosensitizer–metal core@shell nanoparticle. The correlation between time-resolved 1O2 measurements and the experimental and simulated plasmonic optical properties was achieved by comparing the results of four new nanoparticles of different core composition (Au and Ag) and sizes (from 20 to 120 nm in diameter) with the data published in previous studies. Altogether, experiments and modeling in conjunction with statistical analysis revealed that, while the near and far fields work in synergy, it is the near field that dominates the photosensitizer–metal interactions and ultimately dictates the enhancement of 1O2 production. This work improves our understanding of factors important in determining 1O2 enhancement and paves the way to a quantitative description of plasmon–photosensitizer interactions for the rational design of complex nanostructures for boosting 1O2 production.

Singlet Oxygen Photosensitization Using Graphene-Based Structures and Immobilized Dyes: A Review

“…Gold nanostars were also reported to enhance 1 O 2 production of aggregation-induced photosensitizers by 15-fold . The effects of incoherent coupling and near and far-fields is proved to be important on the enhanced 1 O 2 generation. ,, …”

“…304 The effects of incoherent coupling and near and far-fields is proved to be important on the enhanced 1 O 2 generation. 297,305,306 In spite of plasmonic nanoparticles, magnetic nanoparticles have be proven to decrease the 1 O 2 enhancement because they could compete for light absorption with photosensitizers. 307 For example, various core−shell Fe(0)−SiO 2 nanoparticles were synthesized and electrostatically immobilized with [Ru(bpy) 3 ] 2+ , for the photooxidation of citronellol.…”

Impact of Incoherent Coupling within Localized Surface Plasmon Resonance on Singlet Oxygen Production in Rose Bengal-Modified Silica-Coated Silver Nanoshells (SiO2@Ag@SiO2-RB)

“…Furthermore, even detection of 1 O 2 poses challenges in narrowing down on the exact nature of plasmon enhancement. ,, In order to ultimately gain a handle on the rational-design and engineering of advanced materials exhibiting LSPR-induced enhancement, the above questions must be addressed through a systematic investigation of PS photophysics in the presence of a plasmonic nanomaterial with a highly tunable LSPR band. Among a suite of nanomaterials possessing LSPR tunability, such as spheres and rods of various metals, − silver nanoshells have attracted major attention over the past few years for their ease of synthesis, near-infrared (NIR)-spanning plasmonic signature, and LSPR tunability without significant changes to the nanoparticle size. − The latter advantage is especially important for 1 O 2 generation through photosensitization as it ensures a consistent amount of conjugated PS to the nanoparticles and thus provides a basis for the direct observation and comparison of the LSPR effects on photosensitization where the plasmonic signature of the nanomaterial is the only major experimental variable.…”

“…Following the work of Yang and colleagues, we have synthesized a range of SiO 2 @Ag with varying silver shell densities, namely, the incomplete shellsSiO 2 @Ag (i) ; partial shellsSiO 2 @Ag (p) ; and complete, although not entirely defect free, shellsSiO 2 @Ag (c) (Scheme ). Furthermore, using the strategies previously developed by our group, ,,, we have coated these nanoparticles with an outer SiO 2 shell in order to act as a spacer between the LSPR-active metallic shell and the PS (Rose bengal, RB), covalently attached on the surface of the resulting SiO 2 @Ag@SiO 2 nanoparticles. Using state-of-the-art 1 O 2 detection techniques we show that, despite their promising photophysical properties, silver nanoshell-based hybrid particles are poor performers in terms of their 1 O 2 production abilities.…”

Plasmonic enhancement of the antibacterial photodynamic efficiency of a zinc tetraphenylporphyrin photosensitizer/dextran graft polyacrylamide anionic copolymer/Au nanoparticles hybrid nanosystem

“…[13][14][15] The plasmonic enhancement of light absorption by PS molecules located near the surface of metal NPs in a hybrid nanosystem should lead to more effective singlet oxygen production and, hence, to enhanced PDT efficiencies in such nanosystems. [16][17][18][19][20] Also, it has been reported 21 that Au NPs induce antibacterial activity against some pathological bacteria due to their ultra-ne size, which facilitates cellular penetration. In addition, the antibacterial activity of Au NPs might be improved by the generation of reactive oxygen, increasing the oxidative stress faced by microbial cells.…”