A series of uniform and smooth (TCPP/LDH) n films and (TCPP/P 5 W 30 /LDH) n films were fabricated with meso-tetrakis(p-carboxyphenyl)porphyrin (TCPP), Preysslertype polyoxometalate K 12.5 Na 1.5 [NaP 5 W 30 O 110 ]•15H 2 O (P 5 W 30 ), and exfoliated Mg 2 Al−NO 3 layered double hydroxide (LDH) monolayer nanaosheets by layer-by-layer assembly technique. The resulting films were characterized by UV− visible spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and fluorescence spectroscopy. Their third-order nonlinear optical properties were studied by Z-scan measurement with laser pulse duration of 6− 7 ns at a wavelength of 532 nm. The (TCPP/LDH) n films exhibit notable self-defocusing effect and saturated absorption effect which is different from TCPP solution. The optical nonlinearity of films becomes larger with the increase of the number of bilayers. The third-order nonlinear optical coefficient χ (3) of (LDH/TCPP) 50 /LDH is calculated to be (6.4 ± 0.18) × 10 −11 esu. Remarkably, experimental results showed that the (LDH/P 5 W 30 /LDH/TCPP) n /LDH films exhibit much larger nonlinearity than that of the (LDH/TCPP) n /LDH films when n is the same, which is thought to result from the interlayered charge/energy transfer between porphyrin and polyoxometalate although the LDH sheet is electron-inert material.

Third-order optical nonlinearities of ultrathin films derived from cationic phthalocyanine and Keggin polyoxometalates can be well tuned and enhanced.

In order to understand the influence of porphyrin substituents on the nonlinear optical properties of organic–inorganic hybrids composed of an anionic metal–oxygen cluster and a porphyrin cation, porphyrins bearing different functional groups (4-pyridyl, 4-hydroxyphenyl, and 3,4-dimethoxyphenyl) were chosen as prototypes to react with the well-known Keggin-type polyanion α-[PMo10V2O40]5–, which acted as an electron acceptor; this led to formation of three electrostatically bonded disalts with formal formulas of [C40H28N8]­[H4PMo10V2O40]2 (1), [C44H32N4O4]­[H4PMo10V2O40]2 (2), and [C52H48N4O8]­[H4PMo10V2O40]2 (3), respectively. These hybrids were systematically characterized by a variety of means. The nonlinear optical properties of these compounds were studied using the Z-scan technique, conducted with irradiation at λ = 532 nm with a 6 ns duration and a repetition rate of 10 Hz at focus E 0 = 4.2 μJ. While all the hybrids showed an enhanced NLO response compared to their corresponding mother porphyrins, they also exhibited reverse saturation absorption, self-defocusing performance, and an enhancement of the second hyperpolarizability value γ in the order of γ­(1) < γ­(2) < γ­(3), which is parallel to the electron- or charge-donor ability of the functional groups on the porphyrin. Namely, the greater the electron-donor ability of functional groups on the porphyrin, the greater the NLO response.

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