In this letter, we have developed a facile method to enhance the stability of polyelectrolyte multilayers. We fabricate conventional polyelectrolyte multilayers of PAH/PAA through electrostatic layer-by-layer (LbL) assembly and then postinfiltrate photosensitive cross-linking agent 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt into the LbL films. After cross-linking by UV irradiation, the stability of the photo-cross-linked multilayer is highly improved as evidenced by the lack of dissolution under ultrasonication in saturated SDS aqueous solutions for 10 min. Moreover, by taking advantage of the different stability of the LbL film before and after UV irradiation, a patterned surface can be achieved.

In this paper, we have demonstrated a facile strategy to prepare molecularly imprinted layer-by-layer nanostructured films. This strategy has circumvented the requirement of using photocross-linkable polymers, which suffered from tedious synthetic processes in the construction of surface molecular imprinting in layer-by-layer (SMI-LbL) devices. The described SMI-LbL device was constructed by employing the traditional construction procedures of LbL systems, followed by the postinfiltration of bifunctional photosensitive cross-linking agent 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt into the prepared multilayers, and subsequent photocross-linking. A robust SMI-LbL device with high fatigue-resistance was achieved. The preparation conditions have been optimized to achieve repeated unloading and rebinding of the targeting molecule with high fidelity. The combination of templating and cross-linking is the core factor to achieve high fidelity and high efficiency of the SMI-LbL device.

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In this paper, we have developed a facile and general strategy to enhance the stability of multilayers incorporating nanoparticles and the weak polyelectrolyte poly(allylamine hydrochloride) (PAH). Using Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) and Au nanoparticles (Au NPs) as separate model systems, after multilayers of nanoparticles and PAH were constructed employing the layer-by-layer (LbL) technique, 4,4 0 -diazostilbene-2,2 0 -disulphonic acid disodium salt (DAS) was post-infiltrated into the multilayers and subsequent photochemical cross-linking was completed under UV irradiation. The stability of multilayers with Fe 3 O 4 NPs and Au NPs were both improved significantly, and less than 15% of the nanoparticles were lost from the multilayers after an intensive agitation. The UV-visible spectroscopy and atomic force microscopy measurements supported the improvement of the stability of the multilayers. Results and discussionFe 3 O 4 NPs with diameters of 5-10 nm were obtained (Fig. S1 †) through the method of co-precipitation and were incorporated Scheme 1 Illustration for the post-infiltrating process and the photo crosslinking stabilizing strategy.

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