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Sunlight irradiation is the predominant process for degrading plastics in the environment, but our current understanding of the degradation of smaller, submicron (<1000 nm) particles is limited due to prior analytical constraints. We used infrared photothermal heterodyne imaging (IR-PHI) to simultaneously analyze the chemical and morphological changes of single polystyrene (PS) particles (∼1000 nm) when exposed to ultraviolet (UV) irradiation (λ = 250–400 nm). Within 6 h of irradiation, infrared bands associated with the backbone of PS decreased, accompanied by a reduction in the particle size. Concurrently, the formation of several spectral features due to photooxidation was attributed to ketones, carboxylic acids, aldehydes, esters, and lactones. Spectral outcomes were used to present an updated reaction scheme for the photodegradation of PS. After 36 h, the average particle size was reduced to 478 ± 158 nm. The rates of size decrease and carbonyl band area increase were −24 ± 3.0 nm h–1 and 2.1 ± 0.6 cm–1 h–1, respectively. Using the size-related rate, we estimated that under peak terrestrial sunlight conditions, it would take less than 500 h for a 1000 nm PS particle to degrade to 1 nm.
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Optimization of Gold Nanoparticle Synthesis in Continuous‐Flow Micromixers Using Response Surface Methodology
Abstract Gold nanoparticles (AuNPs) were synthesized in microfluidic mixers by means of response surface methodology (RSM). A reverse‐staggered herringbone micromixer was employed and reaction temperature, concentration ratio of reactants, Reynolds number, and pH of chloroauric acid were varied, with desired responses being particle size and peak intensity from UV spectroscopy. RSM was performed by simultaneously optimizing variable ranges to identify the best fit of polynomial equations to experimental data. Results revealed the individual and synergistic roles of each reaction variable on particle size and UV peak intensity, leading to identification of the largest design space. The effect of reaction variables on AuNP synthesis and particle size was confirmed in serpentine mixers.
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- Award ID(s):
- 1659541
- PAR ID:
- 10236452
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemical Engineering & Technology
- Volume:
- 44
- Issue:
- 4
- ISSN:
- 0930-7516
- Page Range / eLocation ID:
- p. 622-630
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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