For the broadband antireflective (AR) coating working in specific wavelengths, the precise control over refractive index and film thickness of each layer is critical to guarantee the peak position locating at the targeted wavelengths. In this paper, a simple sol–gel procedure without post-treatment is used to prepare MgF 2 –SiO 2 hybrid coating with tunable refractive index for the fabrication of tri-layer tri-wavelength broadband AR coating. The MgF 2 –SiO 2 coating with ultralow refractive index of 1.12 is realized through in situ surface assembly of negatively charged silanol groups on vesicle-like MgF 2 particles to obtain porous crosslinking structure. The electrostatic attraction between the negatively charged silanol groups and positively charged MgF 2 colloidal particles plays a key role. Furthermore, the MgF 2 –SiO 2 coating with a wide range of refractive index between 1.20 and 1.44 is achieved by adjusting the addition amount of acid-catalyzed silica sol into the vesicle-like MgF 2 sol. According to the theoretical design, a tri-layer broadband AR coating with refractive index model of 1.12/1.26/1.36 is prepared, which can enhance the transmittance of quartz substrate to near 100% simultaneously at 351, 527, and 1053 nm.
The reaction kinetics for alkaline fading of malachite green (MG) in the critical binary solution 2-butoxyethanol + water and of crystal violet (CV) in the critical microemulsion water/bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/ n -decane with the molar ratio of water to AOT being 30 have been studied by the three-wavelength UV-spectrophotometry at initial reaction stage and various temperatures. It was found that the reaction rates k obs for both above reactions were well described by the Arrhenius equation in the temperature ranges far away from the critical points. The critical slowing down effects were observed in the near-critical regions and the corresponding critical slowing down exponents were determined to be 0.146 ± 0.014 and 0.035 ± 0.006 for the two reactions, respectively. The former exhibited both the dynamic and thermodynamic critical slowing down effects; while the latter showed no thermodynamic singularity. It was attributed to the particular experimental design in this work that made the dimer/monomer droplet equilibrium in the critical microemulsion system no longer affect the reaction kinetics.
In the present study, a novel triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method had been well established to detect perfluorooctane sulfonate (PFOS). We found that crystal violet (CV) could react with PFOS to form 1:1 ion-association complex by electrostatic attraction and hydrophobic effect over a wide pH range (5.0∼11.0) in less than 60 s. The complexes would further self-aggregated into nanoparticles [CV–PFOS]
n
. Based on this phenomenon, not only the absorption and Raman spectra were changed but also the resonance Rayleigh scattering (RRS) intensities were significantly enhanced. And three new RRS peaks located at 327, 492, and 654 nm were clearly observed, respectively. At the same time, it was found that both the enhanced single-wavelength resonance Rayleigh scattering (SW-RRS) and TWO-RRS intensities against the concentration of PFOS showed an excellent correlation. The detection limits for the three single peaks were 27.4 nmol L −1 (13.7 μg L −1 , 327 nm), 27.5 nmol L −1 (13.8 μg L −1 , 492 nm), and 31.4 nmol L −1 (15.7 μg L −1 , 654 nm), and for TWO-RRS method was 5.9 nmol L −1 (3.0 μg L −1 ). Moreover, it could be applied to determine PFOS water samples successfully.
A triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method for rapid and facile assay of perfluorooctane sulfonate (PFOS) based on the interaction with crystal violet (CV) has been successfully established in water samples.
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