We describe the assembly of layer-by-layer films based on the poly(propylene imine) dendrimer (PPID) generation 3 and nickel tetrasulfonated phthalocyanine (NiTsPc) for application as chemically sensitive membranes in separative extended-gate field effect transistor (SEGFET) pH sensors. PPID/NiTsPc films were adsorbed on quartz, glass, indium tin oxide, or gold (Au)-covered glass substrates. Multilayer formation was monitored via UV−vis absorption upon following the increment in the Q-band intensity (615 nm) of NiTsPc. The nanostructured membranes were very stable in a pH range of 4−10 and displayed a good sensitivity toward H+, ca. 30 mV/pH for PPID/NiTsPc films deposited on Au-covered substrates. For films deposited on ITO, the sensitivity was ca. 52.4 mV/pH, close to the expected theoretical value for ion-sensitive membranes. The use of chemically stable PPID/NiTsPc films as gate membranes in SEGFETs, as introduced here, may represent an alternative for the fabrication of nanostructured, porous platfor...