Multifunctional N-doped carbon dots: Integrating corrosion protection and Fe³⁺-responsive warning for steel in acidic environments

Carbon dots have attracted wide interest in corrosion fields due to their superior corrosion inhibition performance, low toxicity and tunable surface functionality. In this work, novel N-doped carbon dots (N-CDs) with dual functionalities—corrosion inhibition and corrosion warning were synthesized via a hydrothermal route and applied to protect carbon steel in strong acid environments. The corrosion inhibition performance of the N-CDs was systematically evaluated using electrochemical measurements, weight loss tests, and surface characterization techniques. Among the synthesized samples, N-CDs derived from L -phenylalanine and L -tryptophan (1:1 molar ratio) exhibited outstanding corrosion inhibition to carbon steel in 1M HCl solution, achieving higher corrosion inhibition efficiency of 96.04% at a concentration of 200 ppm in 1M HCl solution. Mechanistic studies revealed that the inhibition process involved both physisorption and chemisorption, conforming to the Langmuir adsorption isotherm. Moreover, the N-CDs displayed pronounced fluorescence quenching toward Fe³⁺ ions, enabling early-stage detection of corrosion onset. This study presents a multifunctional carbon-based nanomaterial that integrates high-performance corrosion protection with real-time corrosion monitoring, offering new prospects for advanced corrosion control in harsh environments.