Langmuir 2011-08-16

Layer-by-layer assembly and characterization of multilayers of a manganese porphyrin linked poly(4-vinylpyridinium) derivative and poly(styrenesulfonic acid-o-maleic) acid.

Hong-Lei Wang, Qing Sun, Meng Chen, Jun Miyake, Dong-Jin Qian

Index: Langmuir 27(16) , 9880-9, (2011)

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Abstract

Multilayers of manganese(III) porphyrin-linked poly(vinylpyridinium) (MnTMPyP-PVPMe) polyelectrolyte and poly(styrenesulfonic acid-o-maleic) acid (PSS) have been assembled on gold, quartz, and indium tin oxide surfaces by a layer-by-layer (LBL) technique. The assembly process was monitored by measuring their absorption spectra and frequency change after each assembly, both of which confirmed the formation of three-dimensional MnTMPyP-PVPMe/PSS multilayers. The Soret absorption band of porphyrin red shifted about 8 nm in the multilayer compared with that in the dilute aqueous solution. The average mass changes for each assembly of MnTMPyP-PVPMe and PSS were estimated to be about 2.9 and 0.25 μg/cm(2), respectively. X-ray photoelectron spectra revealed that the as-prepared multilayers were composed of S 2p, C 1s, N 1s, O 1s, and Mn 2p, corresponding to polymers of MnTMPyP-PVPMe and PSS. A rough surface was observed after the assembly of MnTMPyP-PVPMe on the gold surface, but it became smoother when the PSS layer was adsorbed. The significant difference in the mass change and film morphology after the assembly of MnTMPyP-PVPMe compared to those after the assembly of PSS was ascribed to the reason that the MnTMPyP-PVPMe polyelectrolyte contained large metalloporphyrin macrocycles, which were axially coordinated to the pyridyl substituents of the PVP polymeric backbones. The cyclic voltammograms revealed two couples of redox waves in the phosphate electrolyte solution at pH 11, which corresponded to the electron-transfer processes of Mn(II)/Mn(III) and Mn(III)/Mn(IV) of polymeric manganese porphyrin MnTMPyP-PVPMe. The charge-transfer process was also investigated. Finally, the present MnTMPyP-PVPMe/PSS multilayers were used as a heterogeneous catalyst for the decoloration of an azo dye.