Carbon dots (CD) have excellent stability and fluorescence activity, and have been widely used in fluorescence methods. However, there are no reports about using CD as catalysts to amplify SERS signals to detect trace sulfate. Thus, preparing CD catalysts and their application in SERS sulfate-sensing are significant. In this article, highly catalytic N-doped carbon dots (CDN) were prepared by a hydrothermal procedure. CDN exhibited strong catalysis of the gold nanoparticle (AuNP) reaction between HAuCl₄ and H₂O₂. Vitoria blue 4R (VB4R) has a strong SERS peak at 1614 cm-1 in the formed AuNP sol substrate. When Ba2+ ions were added, they were adsorbed on a CDN surface to inhibit the CDN catalytic activity that caused the SERS peak decreasing. Upon addition of analyte SO₄2-, a reaction with Ba2+ produced stable BaSO₄ precipitate and CDN, and its catalysis recovered to cause SERS intensity increasing linearly. Thus, an SERS method was developed for the detection of 0.02⁻1.7 μmol/L SO₄2-, with a detection limit of 0.007 μmol/L.
Keywords: N-doped carbon dots; SERS; catalysis; gold nanoreaction.