The Research For The Adsorption And Catalytic Performance Of LDH-Carbon Dot Composites

Compared with the conventional semiconductor quantum dots, carbon dots have the desired advantages of easy functionalization, high surface area, and low toxicity. In addition, the formation of hydrogen bond between the carbon dots and contaminant is attributed to the fact that surface passivated carbon dots contain abundant oxygen-containing functional groups on the surface, which provide many binding sites of hydrogen bond. Furthermore, carbon dots have become a rising star in the catalytic field due to the properties of electron-donating or electron-accepting. However, because of the high-solubility of carbon dots, the practical application of carbon dots in adsorptive and catalytic field has been limited. Therefore, we assembled carbon dots on the surface of layered double hydroxide (LDH). The adsorptive and catalytic behavior of LDH-carbon dot composites have been discussed as follows:(1) A composite was fabricated via direct assembly of positively charged LDH and the carbon dots with abundant oxygen-containing functional groups on the surface. The adsorption performances of the resulting LDH-carbon dot composites were evaluated for the removal of anionic methyl blue dye. The experiment results show that the composites exhibited high uptake capability of methyl blue (185 mg/g), compared with the raw LDH or carbon dots. In addition, the adsorption behavior of this new adsorbent fitted well with Langmuir isotherm and the pseudo-second-order kinetic model. The reasons for the excellent adsorption capacity of methyl blue on the surface of the LDH-carbon dot hybrid were further discussed. A probable mechanism was speculated to involve the cooperative contributions of hydrogen bonding between methyl blue and carbon dots and electrostatic attraction between methyl blue and LDH. This study has opened up new possibilities in fabricating LDH-carbon dot materials in dealing with anionic dye pollutants.(2) A simple and efficient method for the preparation of colloidal composites consisting of carbon dots and dodecylbenzene sulfonate (DBS)-LDH was found. The resulting catalyst can function as an effective heterogeneous Fenton-like catalyst for the decomposition of acidified H2O2 to generate abundant hydroxyl radicals (OH), accompanying with the significant enhancement in the chemiluminescence (CL) signals. We demonstrated that the unique structural configuration of the DBS-LDH-carbon dot composites was responsible for the highly efficient catalytic activities towards H2O2 decomposition. Such heterogeneous Fenton-like catalyst enable the degradation of DBS without any external energy input, showing a promising application for the oxidative degradation of organic contaminants in wastewater treatment.