| Carbon dot (CD) gives rise to their exciting applications in biosensors, biological imaging and ion detection and so on, owing to its low toxicity, biocompatibility and fluorescence properties of the conventional quantum dots. For such applications, embedding QDs into an appropriate matrix is an effective method of preventing their agglomeration because strong flurescence quenching occurs in dry and aggregate states. This method not only ensures the stability of its fluorescence, but also improves its value in practical application. In this study, through CDs combining with Poly(N-isopropyacrylamide) (PNIPAAm) hydrogels and attapulgite (ATP), respectively, these novel materials should be developed and researched, which could simultaneously adsorb and detect metal ion.Firstly, CDs were synthesized by hydrothermal method. The compositions, structures and fluorescence properties of CDs were characterized. According to the results obtained by these characterizations, CDs mainly had the amide functional group. It was spherical, with the average particle diameter of 7 nm. The strong blue fluorescence emission was observed under UV light with the fluorescence quantum yield of 45%. The typical wavelength-dependent PL behavior of CDs was confirmed by the photographs. Furthermore, we investigated the fluorescence quenching effect of various metal ions on CDs. Fe3+ ions had the greatest effect on fluorescence quenching among the metal ions tested. It had significance for CP applications in the material.Secondly, the further functionalization of CD was carried out with glycidyl methacrylate (GMA) to produce PCND. The PNIPAAm-CD hydrogel of a three-dimensional structure was prepared by copolymerizing PCNDs with NIPAAm monomers. Then based on the above, the PNIPAAm-CD-AMPS hydrogel was prepared by adding 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The results indicated that these CDs in the above hydrogels were not leaked out under water. The hydrogels were stable and remained the wavelength-dependent PL property. PNIPAAm-CD and PNIPAAm-CD-AMPS hydrogels showed the higher adsorption property for Fe3+ than the pure PNIPAAm hydrogel. The fluorescence intensities of the above hydrogels significantly decreased after adsorbing Fe3+ under UV light. Finally, the two kinds of hydrogels were obtained which could simultaneously adsorb and detect Fe3+.At last, the CD-KH560 with the-Si-O-CH3 group was synthesized by using CD and silane coupling agent KH-560. The ATP-CD hybrid materials were prepared by the graft polymerization using ATP and KH-560. Interestingly, ATP-CD in the solid state remained a fluorescence emission and the wavelength-dependent PL property. The adsorption value of ATP-CD was slightly higher than that of tATP or approximately equal at the low concentration of Cu2+ and Fe3+. And the adsorptions of ATP-CD and tATP were complete. However, the adsorption capacity of ATP-CD was significantly lower than tATP at the high concentration of Cu2+ and Fe3+. The fluorescence of ATP-CD disappeared at the high concentration (200 mg/L) of Fe3+, which confirmed that it could realize the visual detection of Fe3+ through regulating the amount of ATP-CD.
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