Novel organic heterostructures fabricated with a bilayer consisting of an axially substituted silicon phthalocyanine (R 2 -SiPc) derivative and lutetium bis-phthalocyanine (LuPc 2 ) are investigated for their ammonia sensing properties. Surface and microstructure characterization of the heterostructure films reveal either compact or highly porous surface topography in (345F) 2 -SiPc and Cl 2 -SiPc-based heterostructures, while electrical characterization reveals a strong influence of the axial substituent in R 2 -SiPc on NH 3 sensing capabilities. Electrical characterization further demonstrates an apparent energy barrier for interfacial charge transport, which is higher in the (345F) 2 -SiPc/LuPc 2 heterojunction device. In-depth charge transport studies by impedance spectroscopy further reveal a resistive interface in (345F) 2 -SiPc/LuPc 2 and faster bulk and interfacial charge transport in Cl 2 -SiPc/LuPc 2 heterojunction devices. Different interfacial charge transport capabilities and surface topographies affect NH 3 sensing properties of the two heterojunction devices, in which (345F) 2 -SiPc/LuPc 2 reveals a fast and non-linear response with a limit of detection (LOD) of 310 ppb, while Cl 2 -SiPc/LuPc 2 exhibits a slow, and linear response to NH 3 with LOD of 100 ppb. Finally, different metrological parameters of the two sensors are correlated to the respective gas-material interactions, in which adsorption and diffusion regimes are modulated by the surface topography and hydrophobicity of the sensing layer.

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The versatility of metal complexes of corroles raised the interest in the use of these molecules as element of chemical sensors. The tuning of the macrocycle properties by synthetic modification of the different components of the corrole ring, such as functional groups, molecular skeleton, and coordinated metal, allows the creation of a vast library of corrole-based sensors. However, the scarce conductivity of most of aggregates of corroles limits the development of simple conductometric sensors and requires the use of optical or mass transducers that are rather more cumbersome and less prone to be integrated in microelectronics systems. To compensate the scarce conductivity, corroles are often used to functionalize the surface of conductive materials such as graphene oxide, carbon nanotubes, or conductive polymers. Alternatively, they can be incorporated in heterojunction devices where they are interfaced with a conductive material such as a phthalocyanine. Herewith, we introduce two heterojunction sensors made of junctions of lutetium bisphthalocyanine (LuPc2) with either 5,10,15-tris(pentafluorophenyl) corrolato Cu (1) or 5,10,15-tris(4-methoxyphenyl)corrolato Cu (2). Optical spectra show that after forming the heterojunction, corroles maintain their original structure. The conductivity of the devices reveals an energy barrier for interfacial charge transport, which is larger in the 1/LuPc2 device. The different interfacial barriers is also manifested by the opposite response respect to ammonia: with a 1/LuPc2 behaving as a n-type conductor and 2/LuPC2 as a p-type conductor. Furthermore, the sensors show a high sensitivity respect to relative humidity with a reversible and fast response in the range 30-60%.