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

Abstract

Singlet oxygen (1O2) has been widely produced utilizing nanostructure-based photocatalysts, purposed for photodynamic therapy (PDT), wastewater treatment, and photo-oxygenation reactions. A rational design of heterogeneous photocatalysts is important for a high 1O2 quantum yield under visible-light or near-infrared irradiation. The present review provides insights for graphene-based photocatalyst design by summarizing the mechanism and fundamental aspects of 1O2 sensitization, as well as offers a summary of experimental realization. Subsequently, we go through works done on light-driven 1O2 sensitization utilizing graphitic carbon nitride, carbon dots, graphene quantum dots, and graphene oxide, as well as immobilized organic dyes on polymeric and silica supports, followed by their applications. Moreover, the effect of surface passivation, hybridization with other materials, doping with metal or nonmetal atoms, plasmonic fields, and self-assembly aggregation on the 1O2 quantum yield and 1O2 enhancement factor is discussed. We also provide perspectives for the 1O2 sensitization including applying machine learning (ML) to optimize the plasmonic field and 1O2 quantum yield.

Effective hole conductivity in nitrogen-doped CVD-graphene by singlet oxygen treatment under photoactivation conditions

“…And, followed by the very fast spin-allowed 1 Σ g - → 1 Δ g deactivation that results in the complete formation of 1 O 2 ( 1 Δ g ). Moreover, it has been demonstrated that the graphene doping by heteroatoms, e.g., nitrogen, increase the photocatalytic efficiency 30 , 44 . The photochemical production mechanism of singlet oxygen on graphene:N can be depicted as follows: …”

“…Thus, the completion of the 1 O 2 -treatment process is carried out also on substrate-transferred graphene:N (glass or SiO 2 /Si substrates) by irradiation with Xe lamp. The effectiveness of the photocatalytic aerobic oxidation via singlet oxygen has been exploited by many for the realization of selective oxidative processes towards organic and biological molecules 30 .…”

“…In addition, the presence of these N-functionalities in the graphene structure, besides changing the carrier density (i.e., doping), gives an interesting catalytic activity of the graphene surface, such as the well investigated activated generation of reactive oxygen species (ROS) 28 – 31 . Among these new “catalytic” capabilities, the production of singlet oxygen ( 1 O 2 ) by both (i) activating the dissociation of peroxydisulfate 28 and (ii) the photosensitize excitation of molecular oxygen 30 is of particular interest. In fact, singlet oxygen (also known as singlet delta oxygen 1 O 2 ( 1 Δg)), being a non-radical reactive oxidizing specie, does not intervene on the conjugated double bond as it happens for radical species (oxygen atoms, OH radicals, ozone) and shows higher reactive selectivity also because of its electrophilic nature.…”

The solvent-free mechano-chemical grinding of a bifunctional P25–graphene oxide adsorbent–photocatalyst and its configuration as porous beads

“…23 In turn, graphene oxide brings additional adsorption sites 18 and also acts as a photosensitizer for titanium dioxide. 24 Within the dye series, the degradation of methylene blue and malachite green seems to be more quantitative ($90% degradation reached with TiO 2 @GO-05 : 95). In contrast, methyl orange and Congo red are more difficult to degrade during the advanced oxidation process, as illustrated by the moderate amount of removed dye, which remains at less than 32%.…”

Chemical Vapor Deposition Mechanism of Graphene-Encapsulated Au Nanoparticle Heterostructures and Their Plasmonics

“…Since the plasma oxidation of Au nanoparticles is a critical step facilitating the formation of graphene shells, the effect of plasma conditions (oxidation duration and oxygen partial pressure) on CVD-grown graphene shells was also investigated. These systematic studies allow for optimizing the synthesis of Au@G, where the aim is to achieve high-quality (minimal amorphous carbon content) graphene shells with controlled thickness and to understand the involved growth mechanisms …”