Nanocomposite Indicator-Based High-Resolution Naked-Eye Hue Sensor for Catecholamine Detection

Naked-eye sensing in monochromatic systems is inherently limited in accuracy due to the subjective interpretation of subtle color changes, particularly in catecholamine detection. To address this challenge, we developed a high-resolution multicolor visualization platform utilizing nanocomposite indicators to amplify chromatic signals via dual synergistic colorimetric pathways: (1) catecholamine-concentration-dependent chemisorption protects silver triangular nanoplates (Ag NPLs) from H₂O₂ etching, producing structural color shifts; and (2) Ag⁺ competitively inhibits urease-mediated urea hydrolysis, inducing pH-modulated phenol red chromogenic transitions. The strategic integration of these orthogonal systems created a nanocomposite indicator that expanded the hue range 4.06-fold compared with conventional Ag NPL etching systems, thereby significantly enhancing visual resolution. This platform enabled precise analyte quantification through systematic hue value extraction, successfully detecting catecholamines in PC-12 cell lysates and mouse cerebrospinal fluid. By synergizing enhanced sensitivity with intuitive visual readouts, the multichromatic system advances point-of-care diagnostics for neurological disorders, establishing a clinically viable paradigm for neurochemical monitoring and early disease detection through an optimized, naked-eye sensor design.