| MgAl-Cl-LDHs and MgZnAl-NO3-LDHs with different molar ratio were prepared by traditional coprecipitation method. In order to synthesize dye intercalated hydrotalcite-like compounds (also called layered double hydroxides, short for LDHs) nanocomposites, three kinds of azo-dyes (Ponceau2R, P2R; Methyl Orange, MO and Methyl Red, MR) as anionic guest have been intercalated into MgAl precursors by structure reconstruct and ion-exchange methods. The structures of intercalated products and their optical and thermal stability have been investigated by XRD, FT-IR, TG-DTA, TEM, SEM, UV-vis and elemental analysis, respectively.1. MgAl-Cl-LDHs with the Mg2+/Al3+molar ratio from2:1to5:1were prepared by traditional coprecipitation method. The XRD results indicated the layer distance (0.78-0.80nm) increased with the increase of the molar ratio which related with the charge density of precursor layer. The molar ratio is bigger then the layer charge density is smaller, resulted in weaker interaction of the metal layer and anionic guest of interlayer. SEM and TEM showed LDHs precursors had typical hexagonal structure and the average crystal size is100-200nm. The molar ratio of MgZnAl-NO3-LDHs is n (Mg2+/Zn2+/Al3+)=1:1:1and2:1:1, which also had typical lamellar structure. The layer distance (0.87nmand0.89nm) are larger because of the size of anionic guest in the gallery.2. P2R was intercalated into MgAl-Cl-LDHs precursors with different molar ratio and prepared by ion-exchange method. After intercalated reaction, the interlayer distance of P2R-MgAl-Cl-LDHs expanded to1.67-1.69nm indicated that P2R molecules were intercalated into the gallery of LDHs. SEM and TEM showed P2R-MgAl-Cl-LDHs still maintained typical hexagonal structure. The TG-DTA curves showed the thermal stability of intercalated products improved about80℃more than pure dye. The optical stability of P2R-Mg2Al-Cl-LDHs also improved investigated by UV-vis spectra, absorptivity, lightfastness and so on. The optical stability of intercalated products enhanced by the confinement and protection of host layer to anionic guest. 3. MO was intercalated into MgAl-Cl-LDHs with the molar ratio from2:1to5:1by anion-exchange method. XRD, FT-IR, SEM and TEM indicated that the MO intercalated products had good crystallinity and the laminates of LDHs precursors were not destroyed. The interlayer distance (2.43-2.63nm for MgAl-LDHs) increased compared with the precursors. These results indicated that MO had been intercalated into the LDHs lamellar. The TG-DTA curves revealed that the thermal stability of MO intercalated products were just improved15℃. UV-vis spectrophotometer was used to analyze the change of absorbance followed with the illumination time for MO-Mg2Al-Cl-LDHs. The results indicated that LDHs accelerated the light degradation of MO as a catalyst. The decomposition ratio of MO was65%and95%for MO-Mg2Al-Cl-LDHs, respectively.4. We prepared MR intercalated MgAl-Cl-LDHs with different molar ratio in structure reconstruct method. The interlayer distance of MR-MgAl-Cl-LDHs expanded to2.06-2.12nm, in addition of FT-IR, SEM and TEM characterization, showed MR molecules completely replaced Cl-in the interlayer of LDHs precursors. The TG-DTA curves indicated the thermal stability of intercalated products improved90℃more than pure dye which caused by the confinement of layer and the host-guest intercalation.The optical stability of MR-Mg2Al-Cl-LDHs also improved investigated by UV-vis spectra, absorptivity, lightfastness and so on.The application of azo dyes were confined to their lower optical and thermal stability, it can be solved effectively with the lamellar structure of LDHs. Recent years, azo dyes intercalated LDHs nanocomposites have became a research hotspot as function materials, which played an important role in high-tech areas such as biomedicine, laser technique, electronic industry and photoeletric conversion. |
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