Preparation of mesoporous silica/carbon quantum dots composite and its application in selective and sensitive Hg2+ detection

A luminescent composite was prepared by synthesizing carbon quantum dots (CQDs) in MCM-41, a mesoporous silica material, via a hydrothermal approach under different conditions. The luminescent composite (named MCM/CQDs) was characterized with multiple instrumental techniques including fluorescent spectrometry, UV-Vis spectroscopy, surface area and porosity analyzer, transmission electron microscopy and X-ray diffraction. The preparation condition had an impact on the mesoporous structure of MCM-41, which in turn could influence the properties of CQDs synthesized in MCM-41. The prepared MCM/CQDs samples were used to detect various heavy metal ions in solution. It was found that MCM/CQDs sample prepared at a specific condition was able to detect Hg2+ with high selectivity by reducing the interference of other heavy metal ions. Meanwhile, a high sensitivity of Hg2+ detection was achieved with a detection limit of 0.02 mu mol/L, probably due to the enrichment of Hg2+ by MCM-41 as confirmed by the ICP-MS analysis. This study offered a methodology to develop novel fluorescent sensors based on CQDs embedded mesoporous silica with enrichment ability and tunable fluorescent properties, which enabled application in heavy metal ion detection with high selectivity and sensitivity.