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Synthetic dyes are widely used in various industries, which inevitably leads to increased water pollution. One of the recognized and waste-free techniques for water treatment is photocatalytic purification using semiconductor nanoparticles. However, the debate on how photocatalytic properties can be tuned through structural and morphological parameters using nanoparticle synthesis procedures remains open. In the present work, an approach to regulate UV-light-driven photocatalytic activity of spherical SnO2 nanoparticles using different structural parameters is demonstrated for the first time. Complex characterization of nanoparticles was provided using physicochemical methods with the help of computational methods. Special attention was paid to the development of a protocol of oxygen vacancy accounting within computer calculations for more realistic modeling of the interaction energy between nanoparticle surfaces and organic dye molecules of different natures. The photocatalysis mechanism was investigated according to the developed protocol, including the study of dye mixture kinetic degradation, dye-photocatalyst complex formation, and the ratio of oxygen vacancies and defects. It was shown that 93% of single dye decomposed in 7 min, and degradation of the dye mixture in a real water sample from Neva River achieved 60% after 40 min. It was possible to establish that this proof-of-concept study based on the combination of experimental and computational approaches can help develop the strategy of the rational design of photocatalysts promising for purification of real water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solid-phase microextraction of fluorides on layered double hydroxide nanoparticles. • Cotton rotating disk packed with layered double hydroxide (LDH) nanoparticles. • LDH nanoparticles for in situ formation of the alizarin complexone-Al3+-F– complex. • Layered double hydroxides for smartphone digital image colorimetry. • First procedure for the determination of F– in milk by smartphone-based colorimetry. A novel smartphone digital image colorimetry-based approach was developed for fluoride ion determination, using layered double hydroxide (LDH) nanoparticles (Mg 2 Al(OH) 7) as sorbents for analyte preconcentration and as a source of a central metal ion for a colored complex formation. A cotton rotating disk provided effective retention of the LDH nanoparticles during solid-phase microextraction and elution, excluding time-consuming centrifugation process. In the proposed procedure, the nanoparticles acted as aluminum ion source for alizarin complexone-Al3+-F– complex formation. An image of Eppendorf tube, containing the colored complex solution was obtained by a smartphone and converted, using the RGB model for fluoride ion determination. The procedure had a linear range of 0.20–20 mg L−1 with a limit of detection of 0.06 mg L−1. The developed procedure provided effective fluoride separation from various matrices for its determination by a smartphone without additional sample pretreatment. [ABSTRACT FROM AUTHOR]

In this study, SnO2 nanoparticles modified by copper were found to greatly enhance the chemiluminescence intensity of the luminol–H2O2 system for the first time. The developed approach was applied for the determination of H2O2 as a proof-of-concept example. [ABSTRACT FROM AUTHOR]