UV/Peracetic Acid for Degradation of Pharmaceuticals and Reactive Species Evaluation

Peracetic acid (PAA) is a widely used disinfectant, and combined UV light with PAA (i.e., UV/PAA) can be a novel advanced oxidation process for elimination of water contaminants. This study is among the first to evaluate the photolysis of PAA under UV irradiation (254 nm) and degradation of pharmaceuticals by UV/PAA. PAA exhibited high quantum yields (Φ_254 nm = 1.20 and 2.09 mol·Einstein^–1 for the neutral (PAA⁰) and anionic (PAA^–) species, respectively) and also showed scavenging effects on hydroxyl radicals (<i>k</i>_{<i>^•</i>OH/PAA⁰} = (9.33 ± 0.3) × 10⁸ M^–1·s^–1 and <i>k</i>_{^<i>•</i>OH/PAA^–} = (9.97 ± 2.3) × 10⁹ M^–1·s^–1). The pharmaceuticals were persistent with PAA alone but degraded rapidly by UV/PAA. The contributions of direct photolysis, hydroxyl radicals, and other radicals to pharmaceutical degradation under UV/PAA were systematically evaluated. Results revealed that ^•OH was the primary radical responsible for the degradation of carbamazepine and ibuprofen by UV/PAA, whereas CH₃C­(O)­O^• and/or CH₃C­(O)­O₂^• contributed significantly to the degradation of naproxen and 2-naphthoxyacetic acid by UV/PAA in addition to ^•OH. The carbon-centered radicals generated from UV/PAA showed strong reactivity to oxidize certain naphthyl compounds. The new knowledge obtained in this study will facilitate further research and development of UV/PAA as a new degradation strategy for water contaminants

Asymmetric Ag Nanocrescents with Pt Rims: Wet-Chemical Synthesis and Optical Characterization

A rational and controllable synthetic method for asymmetric nanoparticles in the solution phase is very rare and remains a major challenge. Among pseudo-two-dimensional nanoparticles, plasmonically active asymmetric nanocrescents have been intensively investigated because of their unique strong near-field enhancement and light confinement at the tips. Herein, we demonstrate the synthesis of highly uniform Ag-dominant nanocrescents with Pt rims (AgPt_rim NCs) in an aqueous medium, by adopting Pt split rings as a scaffold for asymmetric growth. The asymmetric nanocrescents collectively exhibited characteristic localized surface plasmon resonance bands, including in-plane and out-of-plane modes, which matched the calculated spectrum of a single Ag nanocrescent, demonstrating the high level of uniformity of the synthesized nanocrescents. We observed light confinement and field enhancement at the sharp tips of the AgPt_rim NCs by comparing their Raman intensity with that from their analogous nanodisks