Plasmonic sensing of CTAB in gold nanorods solution based on Cu(II) ions-mediated H₂O₂ etching effect

Hexadecyltrimethylammonium bromide (CTAB) acts not only as a stabilizer but also as the template in the seed-mediated growth approach, which is significant to the successful preparation of gold nanorods. However, the concentration of CTAB is difficult to determine in gold nanorods solution, especially in the gold nanorods colloids cleaned by centrifugation. In this paper, we have developed a simple, selective, and sensitive plasmonic sensing method for determination of the CTAB concentration in gold nanorods solution by Cu(II) ions-mediated H₂O₂ etching effect. In this sensing, gold nanorods were employed as optical probes, which showed strong longitudinal plasmon band (LPB). The CTAB participated oxidization makes H₂O₂ etch gold nanorods along the long axes. The catalyzed etching leads to the length of gold nanorods being short, resulting in blue shift of the LPB and the sequential color changes. Under the optimal experiment conditions, the blue shift of LPB was proportional to the concentration of CTAB in the ranges of 1–40 mM, with a good correlation coefficient of 0.9865. The recoveries of the CTAB in gold nanorods solution samples ranged from 98.36 to 115.42 %. Therefore, the proposed nano-sensor was demonstrated to be simple, sensitive, and selective, providing an effective alternative for sensing of CTAB in gold nanorods solution.