Rapid virus inactivation by nanoparticles-embedded photodynamic surfaces

The persistent threat of viral epidemics poses significant risks to human health, highlighting the urgent need for antiviral surfaces to mitigate viral transmission through bioaerosols and surface contamination. However, there is still a scarcity of readily accessible antiviral coatings to address this critical concern. In this study, we demonstrate that photodynamic nanoparticle-embedded surfaces can swiftly inactivate both enveloped and non-enveloped viruses. We prepared core-shell structured methylene blue (MB)-loaded SiO2 nanoparticles with a high reactive oxygen species (ROS) yield (0.47 ± 0.02). The superior ROS production was maintained after modifying these nanoparticles onto air filter fibers, likely due to the prevention of aggregation-caused quenching effects. Three viruses, including both enveloped and non-enveloped types, were rapidly inactivated within just 12 min (>6 log units) under medium light intensity (660 nm, 30 mW/cm2). Mechanistic studies revealed that envelope glycoproteins are the primary targets for this rapid inactivation. Thus, photodynamic nanoparticle-embedded surfaces offer a straightforward and adaptable strategy in the fight against viral epidemics.

PDI-Functionalized Glass Beads: Efficient, Metal-Free Heterogeneous Photocatalysts Suitable for Flow Photochemistry

Perylene diimides (PDI) have an extraordinary ability to activate both energy and electron transfer processes upon light excitation; however, their extremely low solubility has hindered their wide use as photocatalysts. Here, we show that the combination of solid-supported PDIs with continuous flow photochemistry offers a promising strategy for process intensification and a scalable platform for heterogeneous photocatalysis. The photocatalyst immobilized onto glass beads is highly efficient, easy to separate, and extremely reusable, with a broad synthetic application range. Using the photo-oxidation of n-butyl sulfide as a benchmark reaction, we demonstrate that immobilized PDI are highly active, outperforming reported homogeneous photosensitizers, and capable of extensive reuse (turnover number (TON) >57,000 over 2 months). Transferring the process from batch to flow results in a 10-fold reduction in irradiation time and an increase in the space-time yield by a factor of 33 (40 vs 1338 mmol-1 h-1 L-1 batch vs flow). What is more, the same catalyst sample can be used for the preparation of a range of sulfoxides, the aza-Henry reaction between nitromethane and N-Ar tetrahydroisoquinolines, and the photo-oxidation of furfural with high catalytic activity. Overall, our work combines the remarkable photocatalytic properties of PDI with inert, easy-to-handle glass beads, producing hybrid materials that are reusable and can be adapted for performing heterogeneous photocatalysis in a range of scalable photochemical reactors.

Structure-Activity Relationship of Benzophenazine Derivatives for Homogeneous and Heterogenized Photooxygenation Catalysis

Singlet oxygen is a powerful oxidant used in various applications, such as organic synthesis, medicine, and environmental remediation. Organic and inorganic photosensitizers are commonly used to generate this reactive species through energy transfer with the triplet ground state of oxygen. We describe here a series of novel benzophenazine derivatives as a promising class of photosensitizers for singlet oxygen photosensitization. In this study, we investigated the structure-activity relationship of these benzophenazine derivatives. Akin to a molecular compass, the southern fragment was first functionalized with either aromatic tertiary amines, alkyl tertiary amines, aromatic sulfur groups, alkyl sulfur groups, or cyclic ethers. Enhanced photophysical properties (in terms of triplet excited-state lifetime, absorption wavelength, triplet state energy, and O2 quenching capabilities) were obtained with cyclic ether and sulfur groups. Conversely, the presence of an amine moiety was detrimental to the photocatalysts. The western and northern fragments were also investigated and slightly undesirable to negligible changes in photophysical properties were observed. The most promising candidate was then immobilized on silica nanoparticles and its photoactivity was evaluated in the citronellol photooxidation reaction. A high NMR yield of 97 % in desired product was obtained, with only a slight decrease over several recycling runs (85 % in the fourth run). These results provide insights into the design of efficient photosensitizers for singlet oxygen generation and the development of heterogeneous systems.

Kinetic effects in singlet oxygen mediated oxidations by immobilized photosensitizers on silica

Singlet oxygen (1O2) mediated photo-oxidations are important reactions involved in numerous processes in chemical and biological sciences. While most of the current research works have aimed at improving the efficiencies of these transformations either by increasing 1O2 quantum yields or by enhancing its lifetime, we establish herein that immobilization of a molecular photosensitizer onto silica surfaces affords significant, substrate dependant, enhancement in the reactivity of 1O2. Probing a classical model reaction (oxidation of Anthracene-9, 10-dipropionic acid, ADPA or dimethylanthracene, DMA) with various spectrofluorimetric techniques, it is here proposed that an interaction between polar substrates and the silica surface is responsible for the observed phenomenon. This discovery could have a direct impact on the design of future photosensitized 1O2 processes in various applications ranging from organic photochemistry to photobiology.

Applications of red light photoredox catalysis in organic synthesis

Photoredox catalysis has emerged as an efficient and versatile approach for developing novel synthetic methodologies. Particularly, red light photocatalysis has attracted more attention due to its intrinsic advantages of low energy, few health risks, few side reactions, and high penetration depth through various media. Impressive progress has been made in this field. In this review, we outline the applications of different photoredox catalysts in a wide range of red light-mediated reactions including direct red light photoredox catalysis, red light photoredox catalysis through upconversion, and dual red light photoredox catalysis. Due to the similarities between near-infrared (NIR) and red light, an overview of NIR-induced reactions is also presented. Lastly, current evidence showing the advantages of red light and NIR photoredox catalysis is also described.