Unraveling Structure-Performance Relationships in Porphyrin-Sensitized TiO2 Photocatalysts

Antimicrobial Photodynamic Therapy: Self-Disinfecting Surfaces for Controlling Microbial Infections

Microbial infections caused by bacteria, viruses, and fungi pose significant global health threats in diverse environments. While conventional disinfection methods are effective, their reliance on frequent chemical applications raises concerns about resistance and environmental impact. Photodynamic self-disinfecting surfaces have emerged as a promising alternative. These surfaces incorporate photosensitizers that, when exposed to light, produce reactive oxygen species to target and eliminate microbial pathogens. This review explores the concept and mechanism of photodynamic self-disinfecting surfaces, highlighting the variety and characteristics of photosensitizers integrated into surfaces and the range of light sources used across different applications. It also highlights the effectiveness of these surfaces against a broad spectrum of pathogens, including bacteria, viruses, and fungi, while also discussing their potential for providing continuous antimicrobial protection without frequent reapplication. Additionally, the review addresses both the advantages and limitations associated with photodynamic self-disinfecting surfaces and concludes with future perspectives on advancing this technology to meet ongoing challenges in infection control.

Sn(IV)porphyrin-Incorporated TiO2 Nanotubes for Visible Light-Active Photocatalysis

In this study, two distinct photocatalysts, namely tin(IV)porphyrin-sensitized titanium dioxide nanotubes (SnP-TNTs) and titanium dioxide nanofibers (TNFs), were synthesized and characterized using various spectroscopic techniques. SnP-TNTs were formed through the hydrothermal reaction of NaOH with TiO2 (P-25) nanospheres in the presence of Sn(IV)porphyrin (SnP), resulting in a transformation into Sn(IV)porphyrin-imbedded nanotubes. In contrast, under similar reaction conditions but in the absence of SnP, TiO2 (P-25) nanospheres evolved into nanofibers (TNFs). Comparative analysis revealed that SnP-TNTs exhibited a remarkable enhancement in the visible light photodegradation of model pollutants compared to SnP, TiO2 (P-25), or TNFs. The superior photodegradation activity of SnP-TNTs was primarily attributed to synergistic effects between TiO2 (P-25) and SnP, leading to altered conformational frameworks, increased surface area, enhanced thermo-chemical stability, unique morphology, and outstanding visible light photodegradation of cationic methylene blue dye (MB dye). With a rapid removal rate of 95% within 100 min (rate constant = 0.0277 min-1), SnP-TNTs demonstrated excellent dye degradation capacity, high reusability, and low catalyst loading, positioning them as more efficient than conventional catalysts. This report introduces a novel direction for porphyrin-incorporated catalytic systems, holding significance for future applications in environmental remediation.

Synthesis of Hybrid Porphyrin(2.1.2.1)s and Their Complexation

Novel hybrid porphyrin(2.1.2.1)s and their boron and copper complexes were synthesized using the "toy bricks" synthetic method. Crystal data, frontier molecular orbital calculations, and electrostatic potential surface maps reveal that hybridization in the porphyrin(2.1.2.1) donor-acceptor unit controls the selective coordination of BF2.

Noncovalent Self-Assembly of Single-Layer MoS2 Nanosheets and Zinc Porphyrin into Stable SURMOF Nanohybrids with Multimodal Photocatalytic Properties

A noncovalent integration of nanosheets of molybdenum disulfide (MoS2) and the zinc porphyrin complex Zn(II) 5,10,15,20-tetrakis(4-carboxyphenyl)porphine (ZnTCPP) through coordination bonding with metal clusters of zinc acetate (Zn[OAc]2) was applied for synthesis of stable hybrid nanomaterial avoiding surface prefunctionalization. The X-ray powder diffraction in combination with the BET nitrogen adsorption method confirms formation of a ZnTCPP-based surface-attached metal-organic framework (SURMOF) with micropores of 1.63 nm on the MoS2 nanosheets. Fluorescence spectroscopy confirmed Forster resonance energy transfer (FRET) between MoS2 and ZnTCPP without contact quenching. Fluorescent trapping with terephthalic acid for hydroxyl radicals and Sensor Green for singlet oxygen was applied for studying the pathways of photodegradation of model organic pollutant 1,5-dihydroxynaphthalene (DHN) in the presence of SURMOF/MoS2. Visible light initiates sensitization through the excitation of ZnTCPP generating singlet oxygen, whereas UV-light promotes either aerobic FRET-mediated "Z scheme" or anaerobic "Type II heterojunction" mechanisms. Owing to its multimodal photochemistry, the SURMOF/MoS2 hybrid showed comparatively high photocatalytic activity in UV-assisted degradation of DHN (keffUV = 4.0 × 10-2 min-1) as well as the antibacterial activity confirmed by E. coli survival test under visible light. Noncovalent self-assembly utilizing coordination bonding in SURMOFs as supramolecular adhesive to avoid surface premodification provides a basis for new types of multicomponent nanosystems with switchable functionalities by combining different 2D materials and chromophores in one hybrid structure.

Surface Modification of ZnO with Sn(IV)-Porphyrin for Enhanced Visible Light Photocatalytic Degradation of Amaranth Dye

Two hybrid composite photocatalysts, denoted as SnP/AA@ZnO and SnP@ZnO, were fabricated by a reaction of trans-dihydroxo[5,10,15,20-tetrakis(4-pyridyl)porphyrinato]tin(IV) (SnP) and ZnO with and without pretreatment of adipic acid (AA), respectively. In SnP@ZnO, SnP and ZnO are likely held together by a coordinative interaction between the pyridyl N atoms of SnP and the Zn atoms on the surface of ZnO. In the case of SnP/AA@ZnO, the SnP centers were robustly coupled with ZnO nanoparticles through the AA anchors. SnP/AA@ZnO exhibited largely enhanced photocatalytic activities for the degradation of anionic amaranth (AM) dye under a visible light irradiation, compared to SnP, ZnO, and SnP@ZnO. The degradation efficiency of AM by SnP/AA@ZnO was 95% within 60 min at a rate constant of 0.048 min-1. The remarkable photocatalytic oxidation performance of SnP/AA@ZnO was mainly attributed to the synergistic effect between SnP and ZnO. This study is valuable for the development of highly effective composite photocatalytic systems in advanced oxidation processes and is of importance for the treatment of wastewater containing dyes.