Roles of Near and Far Fields in Plasmon-Enhanced Singlet Oxygen Production

Abstract

In plasmon-enhanced singlet oxygen ( 1 O 2 ) production, irradiation of a hybrid photosensitizer−metal nanoparticle leads to a significant alteration of the photosensitizer's 1 O 2 yield. The quest for a more rational design of these nanomaterials calls for a better understanding of the enhancement mechanism that, to this day, remains largely unexplored. Herein, we introduce a new methodology to distinguish the near-and far-field contributions to the plasmon-enhanced 1 O 2 production using a tunable model nanoplatform, Rose Bengal-decorated silicacoated metal nanoparticles. By correlating 1 O 2 production to the experimental and simulated optical properties of our nanoparticles, we effectively discriminate how the near-and far-field effects contribute to the plasmonic interactions. We show that these effects work in synergy; i.e., for nanoparticles with a similar local field, the production of 1 O 2 correlates with maximized scattering yields. Our results expound the critical plasmonic aspects in terms of near and far fields for the design of an efficient hybrid plasmonic nanoparticle photosensitizer.

Metal-enhancement study of dual functional photosensitizers with aggregation-induced emission and singlet oxygen generation

“…S10b †). The correlation between ME-SOG and scattering efficiency in our study is in agreement with the literature, 54,79 indicating the important role of the metal NP's scattering efficiency in enhancing singlet oxygen generation. The slight increase in EF SOG for the 2BL Ag@AIE-Y-SOG samples could be attributed to an increase in the intersystem crossing and the competition between different pathways for excited electrons.…”

“…More recently, these localised SPR effects have been exploited to enhance the optoelectronic properties of functional materials, such as uorophores and photosensitizers, leading to a new eld of studying metal-enhanced uorescence (MEF) [30][31][32][33][34][35][36][37][38][39][40][41] and singlet oxygen generation (ME-SOG). [42][43][44][45][46][47][48] To date, several works have been reported to tune the distance between the uorophore and the metallic surface in controlling the plasmonic-enhancement effects. [49][50][51] For example, Liang et al 49 employed the layer-by-layer (LBL) technique to control the distance between the conjugated polymeric uorophore (PFVBT) and silver nanocubes (for up to three bilayers) by using oppositely charged polyelectrolytes for the assembly.…”

“…50 Other than uorescence, singlet oxygen generation is another interesting property of some uorophores (also known as photosensitizer, PS), arising from the intersystem crossing in the excited uorophore. Due to the interactions of the excited uorophore and plasmonic NPs, 42,48,[52][53][54] photostability and SOG rate of the photosensitizers could be enhanced. 43 For instance, Ke and coworkers 55 have reported the simultaneous enhancement of uorescence and SOG of the aluminium phthalocyanine on the surface of Au@silica nanorods.…”

Tailoring Fluorescence and Singlet Oxygen Generation of a Chlorophyll Derivative and Gold Nanorods via a Silica Shell

“…On the other hand, the Ag-NPs have shown more than twice higher enhancement effect than Au-NPs. 33 It has been explained in terms of the far-field contribution to the plasmon-enhance mechanism and evidences the superiority of Ag as the plasmonic core in NPs. The second reason is that we used indirect and independent techniques to estimate ϕ Δ : monitoring of the loss of absorbance of the 1 O 2 trap (DPBF) and detection of heat generated by the investigated system (in time longer than 0.2 μs) related to processes other than the fast depopulation of dye singlet states.…”

Gold Nanostars-AIE Theranostic Nanodots with Enhanced Fluorescence and Photosensitization Towards Effective Image-Guided Photodynamic Therapy

“…In addition, fundamental understanding of the design parameters such as composition [ 32 ], size [ 33 ], and shape [ 29 ] of metal nanoparticles, intrinsic singlet oxygen quantum yield of photosensitizers [ 34 ], as well as the degree of spectral overlap between the extinction of metal nanoparticles and absorbance of photosensitizers play important roles on the performance of colloidal ME-SOG system. However, most of the previously reported colloidal ME-SOG systems either have not studied the fluorescence phenomenon [ 32 , 35 – 38 ] or have observed fluorescence quenching for the ME-SOG samples. [ 15 , 16 ] Indeed, simultaneous enhancement in both SOG and brightness of fluorescence photosensitizer, which is important for image-guided therapy, has rarely been reported [ 39 ].…”