pH-responsive capsule loaded with nitrogen-doped carbon dots for metal corrosion protection

In this study, a stimuli-release system based on mesoporous silica (MSN) loaded with nitrogen-doped carbon dots (N-CDs) as the core material and alginate cheating with Ca2+ as the wall materials were developed. The N-CDs were first synthesized via the solvothermal method, and then MSN@N-CDs were fabricated by stirring for 24 h. The controlled release system (MSN@N-CDs@Alg) was based on alginate cheating with Ca2+. The microstructure and chemical composition of N-CDs, MSN@N-CDs, and MSN@N-CDs@Alg were investigated. The pH-responsive release behavior and anticorrosion performance of the designed system were discussed. Results showed that the prepared N-CDs had a size distribution of 3–5 nm, and the loaded efficiency of MSN@N-CDs was 7.56%. Ultraviolet spectrophotometry measurements confirmed that the prepared capsule exhibited a higher release rate in alkaline conditions. Electrochemical measurements demonstrated that the capsule can release N-CDs intelligently following the corrosion degree of metal to improve the corrosion resistance. This safe, low-toxicity, and simple-to-prepare method can provide a new strategy for metal protection.