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)

Abstract

The use of metal-containing nanoparticles capable of localized surface plasmon resonance (LSPR)-enhanced singlet oxygen (1O2) production, via photosensitization, are currently promising candidates for cytotoxic medical purposes. Despite the ongoing advances in fabricating plasmonic nanomaterials, much of the insight into the fundamental mechanisms governing the photosensitizer (PS)–plasmon interactions remain unexplored. Silver nanoshells (SiO2@Ag) possess seemingly promising optical properties to investigate the underlying LSPR effects on photosensitization, while also raising questions about the nature of LSPR generation in such dielectric-core metallic-shell nanostructures. In the present study, we synthesize and use silica-coated hybrid SiO2@Ag nanoparticles with an outer surface-conjugated PS, and Ag shell densities ranging from ∼50 to >90%, to experimentally investigate these nanostructures’ LSPR-enhanced 1O2 generation properties. Using both direct and indirect 1O2 detection approaches, and with rigorous consideration of 1O2 kinetics, we show that the SiO2@Ag-based structures produce severe inner filter effects in bulk-solution measurements, making them impractical for photodynamic applications. Furthermore, we make a case for the SiO2@Ag nanoparticles’ poor LSPR generation efficiency to be the consequence of the species’ incoherently coupled plasmonic field and resultant lack of enhancement of the nearby chromophore’s photophysical properties.

Enhanced Absorption Performance of Dye-Sensitized Solar Cell with Composite Materials and Bilayer Structure of Nanorods and Nanospheres

“…Compared to aluminum-free SiO 2 , the photoanode based on spherical-shaped aluminum-doped SiO 2 has 37.1% greater absorption. This improvement is attributed to localized surface plasmon resonance, which is comparable with the findings of [30,31]. Surface plasmon resonance creates a larger electromagnetic field on the surface of aluminum nanoparticles, which works in conjunction with plasmons to separate charged dye molecules [32].…”

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.…”

Machine Learning-Aided Design of Gold Core–Shell Nanocatalysts toward Enhanced and Selective Photooxygenation

“…The enhancement factor depends on the overlap between the UV–vis absorption spectra of the 1 O 2 sensitizer and the LSPR band of plasmonic nanoparticles. Other factors include intersystem crossing (ISC) rate, triplet quantum yield, dipole orientation of the sensitizer, , plasmon intensity, and distance ( t ) between the surface of plasmonic nanoparticles and the sensitizers as well as composition, size, and shape of the metal nanostructures. ,− Among these factors, the distance between the surface of the plasmonic nanoparticles and the photosensitizers ( t ) should be below 40 nm to maximize enhancement but not so close as to lead to surface quenching of fluorophores. , So far, several hybrid (gold- and silver-silica) nanostructures immobilized with 1 O 2 photosensitizers have been reported with 1 O 2 EF values between 0 and 12. ,− Although enhanced 1 O 2 generation has been extensively investigated for photodynamic therapy applications, ,− it has rarely been investigated for organic synthesis, − especially for the enhanced photooxygenation reactions and drug synthesis in terms of reaction conversion and selectivity. ,− Therefore, ML can help to rationalize the use of plasmonic nanoparticles to enhance the reaction conversion and selectivity, a long-standing goal in organic synthesis . Moreover, the effect of plasmonic field on the performance of photosensitizers requires a systematic study in terms of intersystem crossing (ISC) energy gap using quantum mechanics.…”