The photosensitised oxidation of amines. Part II. The use of dyes as photosensitisers: evidence that singlet oxygen is not involved

Bartholomew, R. F.; Davidson, R. S.

doi:10.1039/j39710002347

Cited by 37 publications

(33 citation statements)

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“…Another possible explanation of the decreased oxygen inhibition in Nsubstituted amide/acrylate formulations is an oxygen consumption process similar to that described for amines (4,(11)(12)(13)(14)(15)(16)(17). For NVP or NVCL, hydrogen atom abstraction would likely occur on the ring carbon alpha to the nitrogen, followed by consumption of dissolved oxygen through coupling of the pyrrolidonyl radical with an oxygen molecule.…”

Section: Discussionmentioning

confidence: 96%

“…A discussion of the kinetics of free-radical polymerization and competing reactions in the context of oxygen inhibition was given in a previous report (3). A number of techniques have been utilized to combat oxygen inhibition, including use of high intensity lamps/high cure dosages (4)(5)(6)(7)(8), inert atmospheres/sandwiching materials (9,10% and additives such as amines, which have been shown to consume oxygen by a photo-oxidation process (4,(11)(12)(13)(14)(15)(16)(17). In our initial studies (3,18) we confirmed earlier reports (19,20) that NVP dramatically increases the relative rates of acrylate polymerization in air at low light intensities and that a reversible complexation occurs between oxygen and NVP as observed in the UV absorption spectrum (21).…”

Section: Introductionmentioning

confidence: 99%

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N-Vinylamides and Reduction of Oxygen Inhibition in Photopolymerization of Simple Acrylate Formulations

Miller¹,

Hoyle

Jonsson

et al. 2003

ACS Symposium Series

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Cyclic N-vinylamides were found to increase the maximum relative rates of photopolymerization of hexanedioldiacrylate formulations at low light intensities under nitrogen and dramatically under air, while acyclic N-vinylamides and cyclic N-alkylamides were found to have much smaller, though still significant, effects in air. The combination of the cyclic aliphatic amide and N-vinylamide functionalities generally resulted in the maximum benefit for reduction of oxygen inhibition resulting in rapid rates of polymerization in air at low light intensities.While the complete mechanistic explanation of the rate enhancement is still unclear, several possible mechanistic pathways are discussed.

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

N-Vinylamides and Reduction of Oxygen Inhibition in Photopolymerization of Simple Acrylate Formulations

Miller¹,

Hoyle

Jonsson

et al. 2003

ACS Symposium Series

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“…

O_{2}^{\cdot -}

can also arise via a sensitizer radical anion formed by one‐electron oxidation. The generation of

O_{2}^{\cdot -}

that is in equilibrium with

{HO}_{2}^{\cdot}

, as a side product of type I photosensitization, is a more prevalent process . Reactions of

O_{2}^{\cdot -}

can occur with highly oxidizing radicals (addition, reduction) or when there is not an appropriate substrate for its conversion into H 2 O 2 by dismutation (spontaneous or mediated by superoxide dismutase in cells), the precursor of highly reactive

^{\cdot} OH

.…”

Section: Type I and Type Ii Photosensitized Oxidation Reactionsmentioning

confidence: 99%

Type I and Type II Photosensitized Oxidation Reactions: Guidelines and Mechanistic Pathways

Baptista

Cadet

Mascio

et al. 2017

Photochem & Photobiology

622

593

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Here, ten guidelines are presented for a standardized definition of type I and II photosensitized oxidation reactions. Because of varied notions of reactions mediated by photosensitizers, a checklist of recommendations is provided for their definitions. Type I and type II photoreactions are oxygen-dependent and involve unstable species such as the initial formation of radical cation or neutral radicals from the substrates and/or singlet oxygen (1O2 1Δg) by energy transfer to molecular oxygen. In addition, superoxide anion radical (O2•−) can be generated by a charge transfer reaction involving O2 or more likely indirectly as the result of O2-mediated oxidation of the radical anion of type I photosensitizers. In subsequent reactions, O2•− may add and/or reduce a few highly oxidizing radicals that arise from the deprotonation of the radical cations of key biological targets. O2•− can also undergo dismutation into H2O2, the precursor of the highly reactive hydroxyl radical (•OH) that may induce delayed oxidation reactions in cells. In the second part several examples of type I and type II photosensitized oxidation reactions are provided to illustrate the complexity and the diversity of the degradation pathways of mostly relevant biomolecules upon one-electron oxidation and singlet oxygen reactions.

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“…ZnO or Fe/ZnO nanoparticles can recruit O 2 in the initiation mechanism to prevent inhibition of the initiating radicals [24]. Additives such as amines and silanes that consume dissolved O 2 in the system are the most common ways of preventing oxygen inhibition [25,26]. In addition, weak mechanical properties and deprived accuracy of stereolithography resin (SLR) are widespread problems for most desktop-level SLA techniques, restricting their utilization as functional materials [27].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Mechanical and Thermal Properties of Stereolithography 3D Printed Structures by the Effects of Incorporated Controllably Annealed Anatase TiO2 Nanoparticles

et al. 2020

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Fabrication of low-cost, durable and efficient metal oxide nanocomposites were successfully synthesized and reinforced with photo-resin via 3-dimensional printing. Here, we put forward a novel approach to enhance the mechanical and thermal behaviors of stereolithography (SLA) 3D printed architecture by adding TiO2 nanoparticles (TNPs) in different crystalline phases (anatase and rutile), which were obtained at different annealing temperatures from 400 °C to 1000°C. The heat-treated anatase TNPs were scrutinized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, diffusive reflectance spectroscopy (DRS), and transmission electron microscopy (TEM) analysis. Among all the samples, at 800 °C, annealed anatase TNPs exposed a highly crystalline anatase phase, having a low energy bandgap and a comparably high tensile strength (47.43 MPa) and high elastic modulus (2.261 GPa) for the 3D printed samples, showing improvement by 103% and 32%, respectively, compared with the printed pristine stereolithography resin (SLR) sample. Moreover, enhanced storage modulus and tan δ values were achieved via the better interfacial interactions between the incorporated nanofillers and the SLR matrix. In addition to this, enhanced thermal conductivity and thermal stability of the SLR matrix were also noted. The low energy bandgap and nanoscale size of the fillers helped to achieve good dispersion and allowed the UV light to penetrate at a maximum depth through the photo resin.

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The photosensitised oxidation of amines. Part II. The use of dyes as photosensitisers: evidence that singlet oxygen is not involved

Cited by 37 publications

References 0 publications

N-Vinylamides and Reduction of Oxygen Inhibition in Photopolymerization of Simple Acrylate Formulations

N-Vinylamides and Reduction of Oxygen Inhibition in Photopolymerization of Simple Acrylate Formulations

Type I and Type II Photosensitized Oxidation Reactions: Guidelines and Mechanistic Pathways

Enhanced Mechanical and Thermal Properties of Stereolithography 3D Printed Structures by the Effects of Incorporated Controllably Annealed Anatase TiO2 Nanoparticles

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