Figure 3. (A) Schematic illustration for the assembly of
(TA@LDH/PEO)n films by LBL method; (B) UV-vis
absorption spectra of the (TA@LDH/PEO)n (n=10−70) films on quartz glass substrates (inset: the linear relationship
between the absorbance at 213 nm and the bilayer number n ); (C)
Top-view and (D) cross-sectional SEM images of a
(TA@LDH/PEO)50 film.
(TA@LDH/PEO)n multilayer films were fabricated
through layer-by-layer technique on pre-treated substrates (Figure 3A).
UV-vis spectra (Figure 3B) of the as-prepared
(TA@LDH/PEO)n films show two intense absorption
bands at 213 nm and 338 nm, attributed to the characteristic absorption
of TA. The absorbance increases linearly (Figure 3B, inset) relative to
the number of deposition cycles, illustrating the well-proportioned and
gradual growth of the multilayer films. According to the molecular
structure of PEO (Figure S3 C, Supporting Information) and TA (Figure
2B), hydrogen bond network can be formed in the
(TA@LDH/PEO)n films.
Top-view SEM image of a (TA@LDH/PEO)50 film with a
continuous and smooth surface is shown in Figure 3C. Clay alignment in
the multilayer films is clearly observed using cross-sectional SEM
(Figure 3D) image of 50 bilayer film deposited on silicon wafer with a
thickness of ∼865 nm. The image shows a clear layered structure with LDH
nanosheets shown in white lines, which illustrates good dispersity and
high orientation of the LDH nanosheets. The 2D nanosheets with a perfect
parallel orientation to the substrate will play the best role in the gas
barrier function.