Highly responsive hydrazine sensors based on donor-acceptor perylene diimides: impact of electron-donating groups.

Three high-performance hydrazine sensing devices have been developed based on donor-acceptor perylenediimides (PDIs) with strongly electron-donating piperidinyl (PDI-PY), pyrrolidinyl (PDI-PI) and n-hexylamino (PDI-HE) as substituents at the perylene core. These PDI devices, compared with reported PDI molecules, displayed 1-2 orders of magnitude higher sensitivity, short response/recovery time and a lower detection limit towards hydrazine vapour. Experimental results demonstrated that PDI-HE possessed the most excellent sensing performance due to its larger electron density and well-defined crystalline structure with a smaller π-π distance of 3.55 Å, yet, poor crystalline structure, weak π-π orbital overlap as well as a larger interplanar spacing of 3.62 Å led to the poorest sensing performance of PDI-PY devices. This study clearly reveals that electron-donating substituents can remarkably improve the sensing performance of PDI devices by increasing the density of electrons, meanwhile, the steric hindrance of electron-donating groups can modulate the sensing performance by influencing the crystalline structure, π-π overlap and π-π distance. The excellent sensing performance makes donor-acceptor perylenes one of the candidates with the most potential for fabrication of highly efficient PDI sensing devices.