Selective Oxidative Degradation of Organic Pollutants by Singlet Oxygen-Mediated Photosensitization: Tin Porphyrin versus C₆₀ Aminofullerene Systems

Abstract

This study evaluates the potential application of tin porphyrin- and C(60) aminofullerene-derivatized silica (SnP/silica and aminoC(60)/silica) as (1)O(2) generating systems for photochemical degradation of organic pollutants. Photosensitized (1)O(2) production with SnP/silica, which was faster than with aminoC(60)/silica, effectively oxidized a variety of pharmaceuticals. Significant degradation of pharmaceuticals in the presence of the 400-nm UV cutoff filter corroborated visible light activation of both photosensitizers. Whereas the efficacy of aminoC(60)/silica for (1)O(2) production drastically decreased under irradiation with λ > 550 nm, Q-band absorption caused negligible loss of the photosensitizing activity of SnP/silica in the long wavelength region. Faster destruction of phenolates by SnP/silica and aminoC(60)/silica under alkaline pH conditions further implicated (1)O(2) involvement in the oxidative degradation. Direct charge transfer mediated by SnP, which was inferred from nanosecond laser flash photolysis, induced significant degradation of neutral phenols under high power light irradiation. Self-sensitized destruction caused gradual activity loss of SnP/silica in reuse tests unlike aminoC(60)/silica. The kinetic comparison of SnP/silica and TiO(2) photocatalyst in real wastewater effluents showed that photosensitized singlet oxygenation of pharmaceuticals was still efficiently achieved in the presence of background organic matters, while significant interference was observed for photocatalyzed oxidation involving non-selective OH radical.

Tin porphyrin immobilization significantly enhances visible-light-photosensitized degradation of Microcystins: Mechanistic implications

“…Filtration of the resultant solution led to production of [Sn(OH 2 ) 2 (TPy H P)](NO 3 ) 6 crystals as watersoluble tin porphyrin (i.e., s-SnP). Surface loading of aminoC 60 and SnP on silica-based supports were performed and the resultant products were characterized as described in our previous works [26]. AminoC 60 /silica was prepared by covalently loading hexakis aminoC 60 on 3-(2-succinic anhydride)propyl functionalized silica gel via an amide-based linker.…”

“…S3). Immobilization of RB amine hydrochloride was performed according to the procedure used for surface loading of aminoC 60 on the functionalized silica [26]. TGA analysis indicated a weight loss of 4% in the temperature range of 200-420 • C, which corresponds to the sensitizer loading of ca.…”

“…Our previous work [26] demonstrated that two photosensitizers, hexakis C 60 aminofullerene (aminoC 60 ) and tin porphyrin (SnP), were capable of high yield production of 1 O 2 and associated oxidative degradation of pharmaceutical compounds under visible light irradiation. Noteworthily, the direct electron abstraction pathway mediated by SnP (confirmed using laser flash photolysis) caused decomposition of neutral phenolic compounds (e.g., acetaminophen and amoxicillin) that were not susceptible to singlet oxygenation alone by aminoC 60 [26]. Accordingly, exploring the link between photosensitizing activity for singlet oxygenation (or direct electron abstraction) and MC degradation efficiency is important to discern the mechanism(s) underlying the photosensitized oxidation of MCs.…”

Second Test to Send Abstracts

“…These compounds are known to be impressive generators of singlet oxygen [10]. One of the most important applications of them is in photodynamic therapy (PDT).…”

On the mechanism of the [4+2] cycloaddition of 1Ο2 with 1,3-dienes: Identifying the putative biradical/dipolar intermediate by employing the gem-diphenylcyclopropyl group as a mechanistic probe

“…reactions of polymers, 7 in the treatment of wastewater, 8,9 as a non-radical reactive oxygen species (ROS) which is closely associated with tissue damage and various diseases, [10][11][12] and also in photodynamic applications such as blood sterilization, sunlight-activated herbicides and insecticides, and photodynamic therapy (PDT) of cancer. 4,5,13,14 Among the various types of 1 [18][19][20][21][22] Overall, there are two general mechanistic pathways that have been proposed for this reaction, which, in particular, include a concerted and a stepwise pathway.…”