High-capacity adsorbent/sensor from nylon 6 derived carbon dots on SiO2 substrate via one-step surface grafting

[Display omitted] •CDs was for the first time grafted on SiO2 substrate via thermal annealing.•CD-grafted substrate could be used for sensing and as adsorbent simultaneously.•The presence of carboxyl, amino, and hydroxyl groups in CDs was confirmed.•High adsorption of Cu2+ with a density of 2.4×10−5 mg·cm−2 was obtained.•It was functionalized with stearoyl chloride to tailor the surface properties. The fabrication of nanoscale hybrid materials by modifying surfaces with photoluminescent nanoparticles is important for the development of technologically advanced functional surfaces and interfaces. In this work, photoluminescent carbon dots (CDs) were grafted onto SiO2 substrate using a simple one-step thermal annealing method. Two-step methods based on silane chemistry using amidation reaction between CDs and amine-terminated surfaces, and ring-opening reaction between CDs and glycidyl-terminated surfaces, were also developed. The thermal annealing method resulted in a complete monolayer of CDs on SiO2 substrate. The successful grafting by different methods also confirmed that the surface of CDs consisted of –COOH, –NH2, and –OH groups, which have been a subject of debate. The CD-grafted layer was then applied for metal ion sensing and adsorption, showing selective adsorption of Cu2+ with a high adsorption capacity of 2.4×10−5 mg·cm−2. Additionally, functionalization of the CD-grafted layer was also demonstrated toshow itstailoring ability.