title: Highly sensitive and fast responsive fiber-optic modal interferometric pH sensor based on polyelectrolyte complex and polyelectrolyte self-assembled nanocoating.
abstract: A new fiber-optic pH sensor is demonstrated by coating negatively charged polyelectrolyte complex (PEC(-)) nanoparticles, made of sodium carboxymethyl cellulose and poly(diallyldimethylammonium chloride) (PDDA), and positively charged PDDA on the surface of a thin-core fiber modal interferometer (TCFMI) with a layer-by-layer (LbL) electrostatic self-assembly method. The fabricated TCFMI pH sensor has different transmission dip wavelengths under different pH values and shows high sensitivities of 0.6 nm/pH unit and -0.85 nm/pH unit for acidic and alkaline solutions, respectively, and short response time of 30-50 s. The LbL electrostatic self-assembly process of a PEC(-)/PDDA multilayer is traced by quartz crystal microbalance and shows a fast thickness growth. Atomic force microscopy shows the root mean square (RMS) surface roughness of electrostatic self-assembly nanocoating of polyelectrolyte complex/polyelectrolyte is much higher than that of polyelectrolyte/polyelectrolyte due to the larger size of PEC(-) colloidal nanoparticles. The enhanced RMS surface roughness and thickness of the nanocoating can shorten the response time and raise the sensitivity of the TCFMI pH sensor, respectively. In addition, the TCFMI pH sensor has highly reversible performance and good durability.
authors.affiliation: MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science & Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Mingjie
authors.initials: M
authors.lastname: Yin
authors.forename: Bobo
authors.initials: B
authors.lastname: Gu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhao
authors.forename: Jinwen
authors.initials: J
authors.lastname: Qian
authors.forename: Aping
authors.initials: A
authors.lastname: Zhang
authors.forename: Quanfu
authors.initials: Q
authors.lastname: An
authors.forename: Sailing
authors.initials: S
authors.lastname: He