A novel fast response fiber-optic pH sensor based on nanoporous self-assembled multilayer filmsElectronic supplementary information (ESI) available: The UV spectra of multilayer films in construction and deconstruction, and spectra of TCFMI before and after deposition multilayer films. See DOI: 10.1039/c0jm01476a

Three-component multilayer films were prepared by consecutively depositing a polycation blend of poly(4-vinylpyridiniomethanecarboxylate) (PVPMC) and poly(diallyldimethylammonium) (PDDA) with poly(acrylic acid) (PAA). The self-assembly and disintegration behavior of the multilayer films were investigated in details by UV-vis absorption spectroscopy, quartz crystal microbalance (QCM) and atomic force microscopy (AFM). It was found that nanoporous PDDA/PAA multilayer films can be obtained conveniently by partly disintegrating (PVPMC + PDDA)/PAA multilayer films in a 0.15 M NaCl solution. A novel fast response fiber-optic pH sensor was successfully prepared by constructing nanoporous self-assembly multilayer films on the thin-core fiber interferometer (TCFMI) surface. The response time of a fiber-optic pH sensor deposited with nanoporous PDDA/PAA multilayer film (20 s rise time ( t r ) and 15 s fall time ( t f )) was only one-tenth of that with the nonporous PDDA/PAA multilayer film (240 s and 160 s for t r and t f ). Formation of nanoporous multilayer films at physiological conditions and design a novel fast response fiber-optic pH sensor by depositing it on the thin-core fiber modal interferometer (TCFMI).