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Kojic acid is an antioxidant used by the cosmetics industry but the excessive usage of kojic acid may cause harm to human health. Therefore, it is important to detect the content of kojic acid in cosmetic products. In this work, the low-cost and simple paper-based analytical devices (μPADs) based on double-sided adhesive tape were developed for the colorimetric detection of kojic acid. The μPADs were fabricated by dissolving double-sided adhesive tape in toluene and then making the patterned adhesive tape penetrate into the filer paper. Ferric nitrate was used as the reagent to react with kojic acid, and the product of their chelating reaction caused the color change from colorless to orange-red. The ImageJ software was used to analyze the color intensity and the corresponding correction curve was determined. The μPADs for the detection of kojic acid exhibited a wide linear range (0.05 - 4 mM) and the detectable limit was 0.05 mM. The good selectivity and reproducibility were also demonstrated.

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Using EPE as templates and hexamethylenetetramine as hydrolysis agent, precursors of Ni(OH) 2 and Ni(HCO 3 ) 2 are controllably synthesized through adjusting the heating temperature and time. After calcined at 500 • C, NiO nanoparticles have been fabricated from the precursors. The mesoporous NiO prepared from Ni(HCO 3 ) 2 had larger BET surface area than the microporous NiO prepared from Ni(OH) 2 . Both the NiO have good reversibility and capacitance capacity mainly resulted from pseudocapacitive capacitance. At the discharge current density of 500 mA g −1 , the specific capacitance values are 736 and 533 F g −1 for the NiO materials calcined from Ni(HCO 3 ) 2 and Ni(OH) 2 , respectively.