Gold nanoparticles have been used as drug carriers and imaging reagents. The plant extract-capped gold nanoparticles provide better properties than chemically synthesized gold nanoparticles. In this study, Zingiber zerumbet extract-mediated green production of gold nanoparticles (Z. zerumbet@Au NPs) was established. Based on the UV-visible spectroscopy and transmission electron microscope (TEM) results, most Z. zerumbet@Au NPs were spherical. When more Z. zerumbet extracts were added, more spherical nanoparticles were formed. The hydrodynamic size changed slightly along with time, and the average size was approximately 170nm. Capping of Z. zerumbet extract on the surface of gold nanoparticles was confirmed by Fourier transform infrared spectroscopy (FTIR). In general, phenolic compounds or flavonoid compounds were considered to be the reducing agent. However, zerumbone was identified as the reducing agent in this study. The resulting oxidized products were characterized by high-performance liquid chromatography-mass spectrometry (HPLC-MS). As a result, the solvent was proven to be involved in nanoparticle synthesis. Overall, Z zerumbet@Au NPs showed great potential to be used in cosmetic- or biomedicine-related fields.

A rapid hydrogen peroxide analytical method was developed in this study. The developed method incorporated gold nanoparticles (Au NPs) and potassium thiocyanate (KSCN) to improve residual hydrogen peroxide detection performance. Specifically, Au NPs were synthesized and then capped with avocado seed extract (ASE) to form spherical NPs (ASE‐Au NPs) with an average size of approximately 22 nm. The original sample solution color was reddish‐purple. However, when hydrogen peroxide was introduced to oxidize ASE‐Au NPs into ionic species in the presence of KSCN, the solution color gradually changed from reddish‐purple to pink and ultimately became colorless. Ultraviolet‐visible spectroscopy at a wavelength of 533 nm was used to analyze the color change caused by the hydrogen peroxide concentration. The limits of detection and quantification of the developed method were determined to be 6.06 and 20.19 ppm, respectively. The recovery rate of hydrogen peroxide was 90%. Based on these results, a test strip was developed that successfully detected residual hydrogen peroxide in hydrogen peroxide–spiked commercial noodles within 30 min.