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Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag? in Liquid Ammonia Solution.

ABSTRACT: Plasmas with dense concentrations of reactive species such as hydrated electrons and hydroxyl radicals are generated from focusing intense femtosecond laser pulses into aqueous media. These radical species can reduce metal ions such as Au3+ to form metal nanoparticles (NPs). However, the formation of H?O? by the recombination of hydroxyl radicals inhibits the reduction of Ag? through back-oxidation. This work has explored the control of hydroxyl radical chemistry in a femtosecond laser-generated plasma through the addition of liquid ammonia. The irradiation of liquid ammonia solutions resulted in a reaction between NH? and OH·, forming peroxynitrite and ONOO-, and significantly reducing the amount of H?O? generated. Varying the liquid ammonia concentration controlled the Ag? reduction rate, forming 12.7 ± 4.9 nm silver nanoparticles at the optimal ammonia concentration. The photochemical mechanisms underlying peroxynitrite formation and Ag? reduction are discussed.

SUBMITTER: Meader VK

PROVIDER: S-EPMC6017740 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag⁺ in Liquid Ammonia Solution.

Meader Victoria Kathryn VK John Mallory G MG Frias Batista Laysa M LM Ahsan Syeda S Tibbetts Katharine Moore KM

Molecules (Basel, Switzerland) 20180227 3

Plasmas with dense concentrations of reactive species such as hydrated electrons and hydroxyl radicals are generated from focusing intense femtosecond laser pulses into aqueous media. These radical species can reduce metal ions such as Au<sup>3+</sup> to form metal nanoparticles (NPs). However, the formation of H₂O₂ by the recombination of hydroxyl radicals inhibits the reduction of Ag⁺ through back-oxidation. This work has explored the control of hydroxyl radical chemistry in a femtosecond lase ...[more]

PMID: 29495471

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Project description:PurposeThe aim of this study was to assess the effectiveness of the Verion-LenSx guided arcuate incision technique to reduce refractive astigmatism in a pseudophakic population.Patients and methodsA prospective single-arm study was conducted in which one or both eyes of subjects required reduction of 1.0-2.0 D of refractive astigmatism after previous cataract surgery or refractive lens exchange. The surgeon used the refractive cylinder in the eye and the Woodcock astigmatism nomogram for preoperative planning, while the LenSx femtosecond laser with the Verion Image Guided System was used to create all arcuate incisions. The primary outcome measure was the uncorrected monocular distance visual acuity (UCVA). Secondary outcome measures included the change in corneal astigmatism, the change in refractive astigmatism, the best-corrected visual acuity and spectacle independence at distance from preoperative stage to 1 month and 2 months postoperatively.ResultsTwenty-eight eyes of 18 subjects were treated. The best-corrected visual acuity at the 2-month postoperative (PO) stage was not statistically significantly different from the preoperative visual acuity (0.02 logarithm of the minimum angle of resolution [logMAR] in both cases, P>0.05). Uncorrected visual acuity was statistically significantly better at the 2-month PO stage relative to the preoperative value (0.14 versus 0.34 logMAR, P<0.01). The mean change in refractive cylinder from the preoperative stage to the 2-month PO stage was 1.0 D. At the 2-month PO stage, two-thirds of the subjects (12/18) reported that they did not use glasses for distance vision and that their spectacle use for distance vision at 2 months was "lower" or "much lower" than the preoperative stage; in 71% of eyes (20/28), the residual refractive cylinder was ≤0.50 D. Vector changes in keratometric astigmatism were weakly associated with changes in refractive cylinder.ConclusionArcuate incisions made with a femtosecond laser to treat moderate levels of residual refractive astigmatism after previous cataract surgery may reduce dependence on spectacles for distance vision.

Dataset Information

Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag? in Liquid Ammonia Solution.

Publications

Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag⁺ in Liquid Ammonia Solution.

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