Nanozymes-on-a-Bubble with High Signal-to-Noise Ratio Peroxidase-like Activity for Colorimetric Sensing

Nanozyme-based colorimetric sensors have shown their immense potential in environmental monitoring and pharmaceutical quality control. However, achieving interference-free, high signal-to-noise ratio (SNR), and portable detection of the analyte using these sensors remains challenging because their compatibility with multiple optical paths has long been constrained by their inherent dispersibility and optical properties. To address this challenge, we here engineered a multifunctional bubble-scaffolded alloy nanozyme sensor. By leveraging the Hg2+-stimulated peroxidase-like catalytic activity on bubbles, the self-buoyant alloy nanozyme sensor enables colorimetric detection of Hg2+ and ascorbic acid. Notably, this nanozymes-on-a-bubble sensor allows self-separation by self-floating on the solution surface to form a stable coffee ring structure. This unique characteristic avoids optical signal interference originating from the nanozyme itself, thereby significantly enhancing the SNR and optical path compatibility. Furthermore, the sensor integrates with a portable smartphone imaging system, realizing rapid (10 min), low-cost, on-site detection. This assay develops a self-powered nanozyme colorimetric sensor featuring interference-free, high SNR, optical-path compatibility, and portability as a next-generation high-throughput analyzing tool for practical applications.