Multifunctional <i>Tradescantia pallida</i> Derived Copper–Nitrogen Codoped Green Carbon Dots as Nanozyme, Dual Sensor, and Fluorescent Ink for Anticounterfeiting and Smart Textiles

The integration of optical, catalytic, and fluorescent properties in a green eco-friendly product opens avenues for multifunctionality in diverse applications ranging from biosensing and environmental monitoring to smart textiles. Green precursor derived carbon dots (CDs) offer opportunities to tailor their properties to achieve multifunctionality in a single material. Herein, multifunctional copper and nitrogen codoped CDs (Cu,N-GCDs) are reported, which show employability as a nanozyme, colorimetric hydrogen sensor, fluorometric iron sensor, anticounterfeiting agent, and ink for smart textiles. The reported Cu,N-GCDs show peroxidase (POD)-like activity induced by the Cu and N doping. This property is successfully employed in colorimetric H₂O₂ sensing in a wide concentration range of 2 to 1500 mM with a limit of detection (LOD) of 121 μM. The Cu,N-GCDs also exhibited the sensitive and selective fluorometric detection of Fe³⁺ ions with an LOD of 38.95 pM. Moreover, Cu,N-GCDs were employed in making invisible fluorescent ink to draw on paper and cotton cloth, exhibiting their applicability as easy-to-use security technology for information encryption and anticounterfeiting and contributing to aesthetic fashion designing in smart textiles.