Polyelectrolyte-free layer by layer self-assembled multilayer films of cationic phthalocyanine cobalt(II) and carbon nanotube for the efficient detection of 4-nitrophenol

4-Nitrophenol (4-NP) sensors with high sensitivity and reproducibility are desirable for biosafety and environmental monitoring. Herein, cationic tetra-beta-(N,N,N-trimethylaminoethoxy) phthalocyanine cobalt(II)/acid-treated carbon nanotubes multilayer films, marked as (tmaePcCo/CNT)(n), films (n represents the bilayer number), were successfully constructed on glassy carbon electrode (GCE) by a facile, effective layer by layer (LBL) electrostatic assembly method without the assistant of polyelectrolyte. Because CNTs within the multilayer films are beneficial to collect and transfer charges, and polyelectrolyte-free assembly ensures active sites exposing, the obtained (tmaePcCo/CNT)(10)/GCE exhibits excellent 4-NP electrocatalytic performance with good reproducibility and acceptable stability, a wide linear calibration range over 3 orders of magnitude of 4-NP concentrations (1 mu M-1.8 mM) and a low detection limit of 0.2 mu M (S/N = 3), and it can be applied to the quantification analysis of 4-NP under optimum conditions. This work shows that the LBL multilayer films fabricated without polyelectrolyte can provide a valid way to improve the sensitivity and reproducibility of 4-NP sensors. (C) 2016 Elsevier B.V. All rights reserved.