A miniaturized colorimetric-photoacoustic dual-mode device for point-of-care testing of ascorbic acid and ascorbate...

Real-time and rapid detection of ingredients in food has important significance for food safety. However, traditional detection methods not only require bulky and costly instruments but also are often based on single-mode analysis, limiting their accuracy and applications in point-of-care testing. Herein, an integrated and miniaturized dual-mode device based on colorimetric and photoacoustic (PA) principles is developed, using Au@Ag nanoparticles (Au@AgNPs) as signal probe and ascorbic acid (AA) and ascorbate oxidase (AAO) as analytes.

AA can reduce Ag ⁺ into Ag⁰, leading to in-situ growth of Ag shell on the surface of triangular gold nanoplates (AuNPLs) to form Au@AgNPs. Whereas, AAO can catalyze the decomposition of AA, blocking the formation of Au@AgNPs. These changes affect the optical property of Au@AgNPs, further leading to colorimetric and PA changes. A dual-channel test strip was fabricated by immobilizing AuNPLs onto filter paper as the substrate. With a sample volume of 10 μL, linear ranges of 30-500 μM for AA and 10-60 U L^-1 for AAO were obtained. The practicability is further demonstrated through the analysis of several food samples.

This established colorimetric-PA dual-mode device improves analysis accuracy by cross-corroboration between the two modes. Its user-friendly design and minimal sample preparation requirement make it suitable for on-site detection, particularly in resource-limited settings.